Overflow Flow Rate Problems

[BeanAnimal]

Kim I fully understand how water height effects the flow of various types of drains or standpipes. What you don't understand is that moving the bulkhead up or down in relation to the elbow makes no difference. The water is still moving the same vertical distance weather it does so inside or outside the tank. The larger pipe outside the tank REDUCES the velocity of the water by allowing the air to mix with it. The air is being introduced at the TOP, not part way down the back side, there is no "Head Pressure" the way you describe it. This is more or less a free fall.

That said, if the air was introduced part way down, presumably on the back side of the tank at the elbow, then you could measure the head pressure. The water between the down turned elbow and air inject point will be a fill siphon. Following the "durso" design, the next section of pipe will be larger than the siphon section. In other words the water will free fall. In this scenario, you will not have as much control of the siphon via the air that is being injected into the system. You may get be able to get more flow due to the head pressure, but you will have much less control. You will also have more noise due to the added velocity produced by the head pressure. The point begs the question, why not add more standpipes or use larger bulkheads/plumbing instead of trying to shove to much water through a small pipe.

NOW lets go back to the original picture and question. The setup was fully capable of keeping up undr full siphon. This means it could be adjusted by reducing the flow with an air valve.

Bean

 

[Herbert T. Kornfeld]

I'll stick to math Bean. I really dont care to redo our old thread...its simple and everyone knows that depth/pressure is a huge factor in flow through a bulkhead. The overflow rate has very little to do with the length of the downspout/drain pipe. My experiments, experience, and research back that up. If anyone cares to see what Bean is talking about, go here: http://reefcentral.com/forums/showthread.php?s=&threadid=637705&perpage=25&pagenumber=1

Also, as you can see, others are finding better results by using larger diameter durso's to eliminate the vacuum that can benefit an overflow one minute, and back it up the next (and the extra noise it makes is a PITA!). A vacuum is not a reliable way to speed up an overflow...only extra pressure from depth is. The free flow of water through a hole at a given depth is the only reliable way to determine a consistant flow. For a vertical drilled hole, the flow calculations for flow are as follows:

.5" .75" 1" 1.5" 2"
0.5 59.9 134.7 239 538.85 957.97
0.75 73.3 164.9 293.3 659.9 1173.27
1 84.67 190.5 338.6 762 1354.77
1.5 103.7 233.3 414.8 933 1659.2
2 119.7 269 478 1077 1915.9
3 146.6 329.9 586 1319 2346
4 169 381 677 1524 2709
5 426 757 1704

The left column is the depth of the hole in inches, and the top row is the bulkhead diameter. The depth of the hole reflects the amount of water covering the hole as well...so a 1" bulkhead at .5" depth means that the watersurface is at the middle of the hole. As you can see, with depth, the flow rate increases. As you go deeper in water, pressure increases...just like if you were to drill a 1/4" hole towards the bottom of your aquarium...it would shoot across the room, but if you drilled the hole an inch from the water surface, it might just trickle. Keep this in mind. The closer to the surface you make your overflow, the larger diameter opening you need to compensate or the water level will rise until the pressure helps it equalize. This is why people have overflow boxes...its like having a long wide opening for water to flow over and maintain a low water level. Then, down in the box you can have your bulkhead where it can build up a good few inches of pressure (if needed) to help with the flow. What you have done Ruminari is extended your opening to the top, but not enlarged it...so to run 400gph through it, the water will have to rise 1.5"...no longer skimming the surface, and possibly overflowing your tank. You either need to enlarge the intake by increasing the diameter of the intake, or the more effective solution would be to add the box. Otherwise, if you want to keep the 1" inlet and still skim the surface...at a reasonable depth...you will have to decrease your overflow rate under 200gph, and to keep the intake screen, you will have to reduce it even further. In order to keep the standpipe as your overflow, you would need to use reducing connectors to add a piece of at least 1/5" PVC as your intake...if not 2" with mesh/screen guard.

kgross, Bean is right with regards to your post (i think, but from the 3rd person, I can see many people arent being descriptive enough and you both could be interpreted wrong even though you may agree on the same things and both be right). Or maybe you are right...I cant make out what either of you is trying to say...I read one post...go back to another...then go back to interpret things differently...I see half things that are right, and then some things that are very wrong. You are sort of right in that a larger diameter durso COULD increase the flow through the bulkhead below it...if nothing other than because you have increased not the pipe diameter, but the size of the opening at its inlet which is the weakest link. If the flow increases beyond a certain point where the durso becomes submerged...then Bean is right...because then the 1" bulkhead becomes the bottleneck. Having a larger diameter drain-pipe but the same diameter bulkhead will do nothing for increasing his flow...the point that counts is where the intake is...which in this case is not the bulkhead, but the pipe he has added on to it going up to the surface. OTOH, it would help if the pipe that is inside the tank were of larger diameter...increasing the linear overflow area like a box would. If the pipe were 3/4", and the bulkhead 1", then increasing the diameter would help, but being that the pipe in the tank through to the bulkhead is the bottleneck...no increase in the pipe diameter once it passes the bulkhead will help increase the flow...although it does make for excellent sound muzzling. So, long story short, I think what Bean meant to say is that a 40ft long 1" pipe with a 1" hole in the top will flow no better than a 40ft 2" pipe with a 1" hole in the top. But, a 1" hole in the bottom of a 5' long pipe will flow much slower than the same hole in the bottom of a 40' pipe.

 

[BeanAnimal]

Kim..

I just re-read your post and need to add something to my previous post.

You assumption is that the small bulkhead with the large pipe stacked on it is what creates the head pressure. That would be true if the air were not being added. But then that would mean that we would be at full siphon again. There would be no adjustment other than the size of the hole.

I just read richards site for the first time and he states that he is not even sure why the larger pipe works with a smaller bulkhead so well. The smaller bulkhead does allow the water to back up slighty then get sucked through. This slows the velocity of the water down. Somewhat the same as rip-rap in a spill way. He also states that on larger bulkheads there is no nead. This is simply due to the fact that there is so much air and cross section that the water does not slow down.

Bean

 

[Herbert T. Kornfeld]

"I just read richards site for the first time and he states that he is not even sure why the larger pipe works with a smaller bulkhead so well." - Bean

It isnt whats going on at the bulkhead...by making the durso parts larger, you are making sure that the durso's intake isnt the bottleneck anymore...the bulkhead is. This is what Ive been trying to tell you since we first met. By increasing the durso, its intake is no longer the same as the bulkhead's...its larger...enough that the flow calculations can be done from the depth of the bulkhead, not the durso's intake. This is why a deeper overflow box will always outperform a shallow one if plumbed right. Trust me for once...you'll see. Im actually shocked that richards couldnt come up with the reason...its simple. Thats it, Im going to have to write a story with all the info for a future issue of reefkeeping mag.

 

[kgross]

Kim I fully understand how water height effects the flow of various types of drains or standpipes. What you don't understand is that moving the bulkhead up or down in relation to the elbow makes no difference. The water is still moving the same vertical distance weather it does so inside or outside the tank. The larger pipe outside the tank REDUCES the velocity of the water by allowing the air to mix with it. The air is being introduced at the TOP, not part way down the back side, there is no "Head Pressure" the way you describe it. This is more or less a free fall.

You are still wrong, moving the bulkhead up or down in releation to the elbow will effect flow. If the pipe is larger diameter than the bulkhead as a durso needs, the air will not fill up the pipe breaking any siphon in the pipe itself, it will only stop a siphon from creating that siphons from the down elbow all the way down the stand pipe.

First the pipe outside of the tank that you are talking about does not introduce air to the pipe, if it did, it would only serve to break a siphon from the bulkhead down, which would slow down the flow since if you have a siphon though the pipe up the standpipe to the T you will have a lot of "head sucking the water down the pipe (with head pressure negitive pressure works the same as positive only in a different direction.

With the lower velocity of the water in the stand pipe the water level below the introduced air will build up above the bulkhead, when this water level builds up in the stand pipe it creates more head pressure than when the water level does not build up.

That said, if the air was introduced part way down, presumably on the back side of the tank at the elbow, then you could measure the head pressure. The water between the down turned elbow and air inject point will be a fill siphon. Following the "durso" design, the next section of pipe will be larger than the siphon section. In other words the water will free fall. In this scenario, you will not have as much control of the siphon via the air that is being injected into the system. You may get be able to get more flow due to the head pressure, but you will have much less control. You will also have more noise due to the added velocity produced by the head pressure. The point begs the question, why not add more standpipes or use larger bulkheads/plumbing instead of trying to shove to much water through a small pipe.

NOW lets go back to the original picture and question. The setup was fully capable of keeping up undr full siphon. This means it could be adjusted by reducing the flow with an air valve.

Bean

The whole idea of the durso is not to use a siphon to keep up with water flow, since a full siphon of the standpipe will cause extra noise since with the down turned elbow the siphon will draw the water level down (unless the pipe is to small to safely handle the flow) and the system will flush making a lot of noise. If noise is not an issue, just use a straight standpipe that goes up to the water, you will get more flow though it than with the extra elbows on it. To make the durso work correctly you need to size the pipe large enough that it does not try to siphon, instead you can use it to create head pressure above the bulkhead and get more flow through the bulkhead.

Kim

 

[Herbert T. Kornfeld]

oops, that excell chart didnt work so well...well, heres a link:

http://reefcentral.com/gallery/showphoto.php?photo=124520

 

[Herbert T. Kornfeld]

kgross, now you are right on the money. Bean wont accept gravity sometimes...read this other post...he thought a closed loop has the same back-pressure as a sump return too.

http://reefcentral.com/forums/showthread.php?s=&threadid=637705&perpage=25&pagenumber=1

Im still working on him with the whole pressure increasing flow idea. He's very defensive about it.

Your last paragraph Kim...couldnt agree with you more. I find using a vacuum rather than just depth pressure to be a very tricky and noisy way to make a shallow overflow compete with a taller one. It is impossible to maintain, any vacuum will eventually clear the pipe all together and negate the extra flow...and could even overflow the tank before it starts back up (esp if your drain extends below the waterline in the sump so air has a hard time clearing out). It also makes your tank sound like a toilet.

 

[BeanAnimal]

I'll stick to math Bean. I really dont care to redo our old thread...its simple and everyone knows that depth/pressure is a huge factor in flow through a bulkhead.

We all agree that head pressure is a factor on the flow through a hole in a tank. You seem to forget the fact that we are not talking about a tank. We are talking about free falling water.


The overflow rate has very little to do with the length of the downspout/drain pipe. My experiments, experience, and research back that up.


This again, has NOTHING to do with this thread. I don't think you will find that I said any different either. You are trying to make arguements where they don't even exist.


Also, as you can see, others are finding better results by using larger diameter durso's to eliminate the vacuum that can benefit an overflow one minute, and back it up the next (and the extra noise it makes is a PITA!).

Again, this is obvious. The closer to free fall you are, the less air needs to be sucked in to keep the system in balance. There never was an arguement here.


A vacuum is not a reliable way to speed up an overflow...only extra pressure from depth is. The free flow of water through a hole at a given depth is the only reliable way to determine a consistant flow. For a vertical drilled hole, the flow calculations for flow are as follows:

.5" .75" 1" 1.5" 2"
0.5 59.9 134.7 239 538.85 957.97
0.75 73.3 164.9 293.3 659.9 1173.27
1 84.67 190.5 338.6 762 1354.77
1.5 103.7 233.3 414.8 933 1659.2
2 119.7 269 478 1077 1915.9
3 146.6 329.9 586 1319 2346
4 169 381 677 1524 2709
5 426 757 1704



Your table is pointless as it does NOT descrivbe the system we are talking about. You also need to be very careful in your word choice. Free flow usually denotes flow over a weir, not flow through a restriction.


The left column is the depth of the hole in inches, and the top row is the bulkhead diameter. The depth of the hole reflects the amount of water covering the hole as well...so a 1" bulkhead...

Your a broken record... Once again, this is not the model a durso work on. Why can you not understand that? You are describing the effects of static head on a hole in a tank. (a bulkhead). A durso does not work on this principle. You just don't seem to understand that the pipe outside the tank is no different than the pipe inside the tank. If we were talking about a fully submerged bulkhead without any air being introduced, then your table would work.

...it would shoot across the room, but if you drilled the hole an inch from the water surface, it might just trickle. Keep this in mind.

Herbert, once again.... the sump is at the same level. The water is more or less free falling because air is introduced at THE TOP of the standpipe. Your example does not fit the model here at all. It is again obvious that a hole at the bottom of the water tower will shot water further than a hole at the top.



The closer to the surface you make your overflow, the larger diameter opening you need to compensate or the water level will rise until the pressure helps it equalize. This is why people have overflow boxes...its like having a long wide opening for water to flow over and maintain a low water level. Then, down in the box you can have your bulkhead where it can build up a good few inches of pressure (if needed) to help with the flow.

Again, you don't undersand the difference between free fall and siphon/head pressure. Also following your logic, the overflow box is a net loss in head pressure because you lose a few inches from the static height of the tank.

I will not disect any more of the post (other than the last paragraph) , it just takes to long.


1" hole in the bottom of a 5' long pipe will flow much slower than the same hole in the bottom of a 40' pipe.

What I said was that if you take two vertical pipes with the following parameters:

open at the top
closed at the bottom
both pipes have a 1" bulkhead at the very bottom.
1st pipe is 40 FEET in diameter
2nd pipe is 2 INCHES in diameter

BOTH bulkheads will have the same flow. This of course is what your "table" shows. In other words, a 1" hole 18" from the surface of the hoover dam will flow exactly as much as a 1" hole 18" from the surface of your tank. The water will "shoot out" the same distance from each hole.

Bean

 

[BeanAnimal]

"I just read richards site for the first time and he states that he is not even sure why the larger pipe works with a smaller bulkhead so well." - Bean

It isnt whats going on at the bulkhead...by making the durso parts larger, you are making sure that the durso's intake isnt the bottleneck anymore...the bulkhead is. This is what Ive been trying to tell you since we first met. By increasing the durso, its intake is no longer the same as the bulkhead's...its larger...enough that the flow calculations can be done from the depth of the bulkhead, not the durso's intake. This is why a deeper overflow box will always outperform a shallow one if plumbed right. Trust me for once...you'll see. Im actually shocked that richards couldnt come up with the reason...its simple. Thats it, Im going to have to write a story with all the info for a future issue of reefkeeping mag.

DEPTH CALCULATION CAN NOT BE DONE AT THE DEPTH OF THE BULKHEAD. Simply because of the air being introduced. The air is the thing your missing herbert.

In fact, why would you use a smaller bulkhead. Following your example, a larger bulkhead and pipe with a restriction right at the sump would be the best bet. Ahh but then we have to introduce even more air to prevent a full siphon!! Noise once again. Do you see where your logic breaks down and you contradict yourself?

You are modeling a hole inn a tank, not a durso standpipe. It's that simple.

 

[BeanAnimal]

Kim,

Again, I understand we are trying to avoid a full siphon. It is also very obvious that if the bulkhead is restrictive enough water will stack up and create head perssure. Lowering the bulkhead is no different than keeping the pipe after the bulkhead the same size or smaller.

You also re-iterated my point about adding air later in the plumbing.

Bean

 

[Herbert T. Kornfeld]

You talk in circles Bean, first you say we are talking about free-falling water...then when I post rates on a chart, you claim we are not...

Free flow, in this case means water that is flowing through a hole at a given depth. If you take a vat, and make equal holes at 1" deep, 6" deep, 12" deep, etc...the water flow will increase with depth as it comes out. I mean free-flow as in NOT adding in calculations for the pipe once the water makes it through the bulkhead. The pipe diameter should be big enough that there is no suction at this point, and water 'free-falls' to the sump. The sump's height relative to the tank's level means nothing.

And about the durso...you are right in that it might not be the way YOUR durso works...but that does not mean that it applies to all. The calculations and my comments are 100% applicable...you just wont give up these ideas of yours. Im sick of trying to get through to you. These things do apply...you just wont accept them because you only know one example and you keep repeating it over and over again...but your situation does not always apply. Kim, can you make sense of this? This guy is just too thick for me. I know Im right. I can run simulations on the computer, and do the equasions all I need to, even make experiments to prove it...and he still wouldnt accept it.

A durso is a hole in the tank...it just changes where the bottleneck is...or it might not depending on how its done. You are just seeing what you want to Bean...others can read this and know what I'm saying. What will it take? A live TV special with me telling you and doing live demonstrations?

Im not missing the air...it doesnt count with pressure like it does with a vacuum. Think about it...there is a point where you increase the diameter of the durso so that the most restrictive point is no longer the durso intake but the bulkhead itself...allowing for more flow! Lets say that the durso is made of 6" pipe, and goes to a 1" bulkhead at the overflow bottom. This will have a higher max flow than a durso done with all 1" piping. Why? Cuz the max flow at even just a few inches of depth of a 6" pipe exceeds that of the 1" bulkhead at even say, 24" of depth. That is the reason for the other guy who used larger pipe getting a higher flow rate by using larger diameter pipe for a durso. Its easy to explain. It does matter Bean...THATS HOW THE CALCULATION CAN BE DONE AT THE DEPTH OF THE BULKHEAD>>>WHEN THE DIAMETER OF THE PIPE AT INTAKE LEVEL HAS A HIGHER FLOW CAPACITY THAN THE BULKHEAD AT DEPTH>>THE BULKHEAD BECOMES THE NEW BOTTLENECK. Otherwise your overflow box wouldnt work. The air doesnt matter in this case. Thats why pressure at depth can force more water through a hole than a vacuum>>>> The pressure of water will displace the air if it needs to to keep up. The vacuum of the drainpipe will only suck more air and therefore not be able to keep up as well. Why tall overflows can always outperform shallow ones. Why larger diameter pipe / overflow boxes are needed to keep up at the surface cuz they dont have the benefit of head pressure.


No contradiction...you arent looking at a broad enough scale.

 

[Herbert T. Kornfeld]

Ruminari,
ok, what the point of the table is as far as you are concerned...

It shows what you can do to increase your overflow's throughput by manipulating the area of the opening at the water surface, or what your maximum throughput would be at a given depth with that bulkhead if you go with an overflow box. If you were to remove the pipe that extends to the surface of the tank, and replace it with a pipe that has a diameter of say, 2", your flow would be raised to either the 1" bulkhead at 4" of water depth (isnt that about what it is?) or the flow of a 2" opening at say, 1/4-1/2" depth...which ever rate is lower. So, the flow through a 1" hole at 4" depth is 677gph, and the flow of water at the top of the new 2" pipe would be upwards of 900gph with a water level that is about 1/2" above the pipe's inlet height. Take away some flow for the screen or teeth, but you will still have alot of flow...more than 400gph...up to 677gph to be exact (given that your 1" bulkhead is 4" or more from the water surface).

Or, you could make an overflow box...even just a 6"w x 4"d x 6" tall one would make your linear overflow, even with 1/4" slots and 3/4" teeth to be about 2.5" long, meaning your water level would rise about 1/2" from the bottom of the slots and be able to accomidate over 1000gph at the box's top, but the 1" bulkhead at 4" depth would max out at the same 677gph limit.

Bottom line is, you can get over 600gph through that 1" bulkhead, but you have to increase the linear overflow capacity with larger pipe or a box at the water surface. That 1" pipe would make the water rise a couple inches to keep up if used alone as the overflow...and not even skim the surface (unless it makes a vortex!).

Yeah Bean, that table was useless.

 

[BeanAnimal]

I am going to be frank. Your literacy skills are lacking and your only means of debate is to put words in peoples mouths. It is not I that am talking in circles. You are simply trying to fuel a pointless arguement with out of context remarks and information.

ONCE AGAIN it is well established that the deeper a 1" hole is, the more water will be forced through it. You act as if I don't understnad this and then base your entire arguement on this premise. So right off the bat your wrong, as is the foundation of your comments. You keep pointing this model out, but WHAT YOUR THICK SKULL DOES NOT GET.... IS THAT THIS IS NOT HOW A DURSO WORKS. You AGAIN are applying the wrong physics to the pipe in the picture at the top of this thread.

Let me say that again. Your barage of posts do not correctly describe what is going on in the picture at the top of this thread. You also don't seem to be able to relate my comments to the picture or the thread itself. Your "information" is correct, but it does not apply here. Good grief. Lets say it one more time in case you still don't get it. The numbers in your table are correct, but they don't apply here.

Regarding applying them to a "durso"... if you apply your model (a hole under water), then you no longer have durso. You just don't get it.

Regarding your pipe sizes in relation to the bulkhead sizes... You are trying to tell me that a 40 foot tall 10 foot diameter pipe with a 1" bulkhead in the bottom will push more water through it than a 40 foot tall 1 foot diameter pipe, with the same bulkhead? If this is what you think, then you really need to go back to 6th grade and retake basic science.

Herbert, the durso intake is not the restriction. If they system can handle the flow at full siphon, then the "restriction" that tunes they system is AIR. If the intake is smaller than the bulkhead then the system will still work, as long as it is big enough to handle the flow at full siphon. You are making up "stuff" as you go again. With each and every post your talk more out of your ***.

Now to the next point... I honestly don't wish to continue this thread. I don't like you, and your circular reasoning and inability to understand the context of this debate are a waste of my time. You may be able to shout down or spin other people, but your utter lack of understanding and communication skills does not go very far with me. Enjoy yourself and please don't misinform to many people with your self inflated ego and made up science. I suggest you build several standpipe setups out of clear PVC so that you can observe how wrong you are. You mention a computer model.... but I highly doubt you are going to be able to simulate a durso standpipe WITH THE AIR. Submerged drains are easy, vortex or non laminar systems are much to complicated to model with basic software. Your talking out from your bottom side again.

Bean

 

[wave_happy]

Gee Whizz!!!

:mixed:

 

[Herbert T. Kornfeld]

"I am going to be frank. Your literacy skills are lacking and your only means of debate is to put words in peoples mouths. It is not I that am talking in circles. You are simply trying to fuel a pointless arguement with out of context remarks and information."

-Bean

Right back at you. Please keep your remarks on the subject at hand. Trying to take cheap shots and making personal remarks does not help you prove any of your points...it gets you banned by a moderator.

"ONCE AGAIN it is well established that the deeper a 1" hole is, the more water will be forced through it. You act as if I don't understnad this and then base your entire arguement on this premise. So right off the bat your wrong, as is the foundation of your comments. You keep pointing this model out, but WHAT YOUR THICK SKULL DOES NOT GET.... IS THAT THIS IS NOT HOW A DURSO WORKS. You AGAIN are applying the wrong physics to the pipe in the picture at the top of this thread."

-Bean

Well Bean, how does a durso work then? You are good at telling other people they are wrong...but where is your version then? Its a standpipe with a downward facing intake and air inlet for the vacuum that the water creates (or so I think). This setup with the air is used to reduce the noise that the standpipe would make if its opening to the outside were larger. Right? Well, when you add that durso standpipe the point of greatest restriction becomes the top of the durso if the durso's pipe diameter is the same as the bulkhead it goes to...many inches or feet from the top. What that other person did by adding a wider diameter standpipe and intake is alleviate this restriction. The chart is the tool that shows this. The durso's top inlet is no longer the point of greatest restriction...the bullkhead is once again (at the bottom of the overflow). There are other reasons for the greater flow here, like the lower vacuum of the water in a larger pipe(water flows aroung the outside and lets air pass through the middle without getting sucked in), which aids in the flow of the water because of less air being sucked in. Hey, disagree all you want, but Im not the only one saying that this happens. The proof seems to outweigh your attacks. The larger diameter durso is really like adding an inverted overflow box inside another...its greater linear overflow area helps with flow.

"Let me say that again. Your barage of posts do not correctly describe what is going on in the picture at the top of this thread. You also don't seem to be able to relate my comments to the picture or the thread itself. Your "information" is correct, but it does not apply here. Good grief. Lets say it one more time in case you still don't get it. The numbers in your table are correct, but they don't apply here. "

-Bean

Well, Bean, the point was that this enlarged durso is very much the same condept that needs to be applied to this overflow...which is an imcomplete durso. The concept that can be used is that he obviously needs to enlarge his pipe at the intake level to take care of his problem...or add an overflow box. That is the relation to be made.

"Regarding your pipe sizes in relation to the bulkhead sizes... You are trying to tell me that a 40 foot tall 10 foot diameter pipe with a 1" bulkhead in the bottom will push more water through it than a 40 foot tall 1 foot diameter pipe, with the same bulkhead? If this is what you think, then you really need to go back to 6th grade and retake basic science. "

-Bean

Well Bean, you are using extremes here, so let me make the relation more realistic. A 4 foot tall standpipe that is 1" in diameter and drains through the bottom at a 1" bulkhead will have a lower flow rate than the same setup with a 2" pipe & 1" bulkhead. That is the whole point of what Im saying. That is why the larger diameter durso works better than the narrow one...that is what needs to happen to cure the problem in the current thread.

"Herbert, the durso intake is not the restriction. If they system can handle the flow at full siphon, then the "restriction" that tunes they system is AIR. If the intake is smaller than the bulkhead then the system will still work, as long as it is big enough to handle the flow at full siphon. You are making up "stuff" as you go again. With each and every post your talk more out of your ***."

-Bean

Well, the point of a durso is not to have a siphon, but to muzzle noise. A vortex or vacuum does not always happen depending on the pipe diameter - flow ratio, and can in fact backfire causing a backup as it is near impossible to maintain constantly. The air isnt there to aid the siphon, the air is there because it has to be, and the small air inlet just because if the top was left open it would make lots of noise. A durso is not some device to increase overflow rates. I think Kgross said this as well on the last page. The durso is in fact the restriction. If that was not true, like you say above, removing a durso when its working would result in the water level staying at the same height after removing the pipe...but this isnt true...it drains down to the bottom of the overflow doesnt it? How could it not be the restriction? Making the durso pipe larger offsets this restriction...But hey, dont take my word for it...it seems others are experiencing the same results.

"Now to the next point... I honestly don't wish to continue this thread. I don't like you, and your circular reasoning and inability to understand the context of this debate are a waste of my time. You may be able to shout down or spin other people, but your utter lack of understanding and communication skills does not go very far with me. Enjoy yourself and please don't misinform to many people with your self inflated ego and made up science. I suggest you build several standpipe setups out of clear PVC so that you can observe how wrong you are. You mention a computer model.... but I highly doubt you are going to be able to simulate a durso standpipe WITH THE AIR. Submerged drains are easy, vortex or non laminar systems are much to complicated to model with basic software. Your talking out from your bottom side again."

-Bean

Well Bean, Ill send you a PM when the results are all in. I am using a 20H with a shallow box overflow in one end...1" bulkhead 3" from the surface in a 4"x6"x6" overflow box. At the other end is a full height overflow with a bottom bulkhead. The standpipes and plumbing can be swapped out on the fly, but both go down to a rubbermaid vat with a Mag18 return pump. I am simply awaiting for my flow meter to arrive so I can report something more than what the the bypass valves are set to at any given time on the return pump. So far, everything is coming up close to predictions. The tall overflow gets 3x the throughput of the shallow one (it can take about 1500gph, but the shallow one tops out at about 500gph). The wide 2" durso allows for the full flow as well but the 1" one cuts it back to 1/3 of that again. Its all about finding the point of greatest restriction and eliminating it. Air is a bystander and just something to be muzzled. The Richards results also show this to be true.

 

[Herbert T. Kornfeld]

"Kim without creating another huge thread with a lot of bad information. Pipe Diameter has NOTHING AT ALL to do with head pressure. This is the first thing you learn when dealing with fluid or "head pressures" A 40 foot diamter pipe with a 1" diamter hole in the bottom will not push the water through any faster than a 2" diamter pipe with a 1" hole in the bottom."

-Bean

You posted this a while back, and while it is somewhat correct, to apply it to what we have here you should also mention that a 1" diameter pipe with a 1" diameter hole at the bottom (assumed that all are the same height) would have much less flow than either of the pipes above (unless the water height is allowed to build up even higher from the top of the durso). In both of the examples above, the point of greatest restriction is the hole in the bottom of the pipe. But with a 1" pipe, the most restrictive point is moved up to the top of the pipe since it is the same size as the bulkhead/hole. And in this respect, head pressure doesnt build up like in a larger diameter pipe...as the whole pipe, hole, etc...is the same size. With a larger pipe, head pressure would build up. So with the two examples you give pipe diameter might have nothing to do at all with head pressure...but we arent using 40' diameter pipes here...we are using 1" to 2" pipes...and then pipe diameter does have to do alot with head pressure. That is also what is important here.

 

[BeanAnimal]

Herbert: I lied.. this is going to drive me nuts.

Lets just take a point at at time.

You state the pipe diameter has something to do with head pressure. You had better check your physics book. This is 100% WRONG. It does not matter if the pipe is 1" or 1' diameter, the head is the same. Head does not depend on volume. Head depends on the height of the water column and barrometric pressure.

You also state that air is a bystander. This is also not at all the case. We know that a full siphon will flow more than a pipe with air and water. The air takes up room and also interupts the water column. The system goes from a siphon (head pressure) to a free fall or open flow. The flow through the downpipe changes from laminar to turbulant, reducing the velocity even more.

Mull this over for a bit....We will disect the bulkhead/pipe diameter issues later. I think you may be suprised if you look at drawings.

I have a damsel to catch.

Bean

 

[Herbert T. Kornfeld]

Ok, agreed, one at a time.

"You state the pipe diameter has something to do with head pressure. You had better check your physics book. This is 100% WRONG. It does not matter if the pipe is 1" or 1' diameter, the head is the same. Head does not depend on volume. Head depends on the height of the water column and barrometric pressure."

-Bean

Pipe diameter does have something to do with head pressure. Like the example I gave above, if the standpipe is too restrictive, the head pressure never has a chance to build up because the standpipe drains faster as the water falls further. A good example, however unlikely, would be a 3/4" standpipe on a 1" bulkhead...no head pressure exists because the water never even builds up enough to gain depth pressure, right? But with a 2" pipe on a 1" bulkhead, this is not the case. In this case the water can drain faster in the 2" part than the 1" part...so head pressure builds up (granted, if the flow is more than the 1" bulkhead could easily pass w/o buildup).

So a good rule would be that if the standpipe is equal to or less than the bulkhead diameter, there is no head pressure....but if the standpipe diameter (or durso, whatever) is greater than the bulkhead, then head pressure builds up. To restate what you said above...Head can depend on volume...not enough volume, no head at all. And since it is a ratio with pipe diameter...pipe diameter also has a role in head pressure...too much pipe diameter, no buildup, no pressure...nothing but FREE FALL <<<there it is, LOL!

Now, because the 1" standpipe is a mere 1" at the top, this is just as restrictive as the lower point (proven by the fact that water doesnt build up lower in the pipe anywhere, right?) So this pipe has its most restrictive point starting at the top of the durso/standpipe. But with a 2" durso/standpipe, the water flows with less restriction above...but can build up above the bulkhead...the bulkhead is now the most restrictive point. For these reasons, now do you see why in the other thread why I said a tall overflow will always outperform a shallow one of the same bulkhead size?

"You also state that air is a bystander. This is also not at all the case. We know that a full siphon will flow more than a pipe with air and water. The air takes up room and also interupts the water column. The system goes from a siphon (head pressure) to a free fall or open flow. The flow through the downpipe changes from laminar to turbulant, reducing the velocity even more. "

-Bean

I think the reason why you do things like this is something I see you often mentioning...using your durso as a siphon. Why, as its near impossible to maintain even with constant adjustment? How, for that matter, do you deal with the extra noise? The air on a durso is restricted in its inlet diameter for noise...but restricted in volume more than if you had an open top...thats not a good idea. If air isnt left as a bystander...and you are restricting it to speed up your overflow...you might want to reconsider your system...as I agree with you on the whole laminar to turbulent part...where the pipe purges and velocity is reduced. This wasnt what dursos were meant for...in fact, you are nullifying their designed use...to eliminate noise...as every time the siphon purges its breaking the water barrier and letting noise out. I think I see why you and I disagree...youve been using durso's to speed up your overflow rate by limiting the air (am I getting this right). In which case most of the stuff you are saying is true under situations where everything is nothing but a vacuum that relies puerly on the height of the drainpipe. Ahhh...I think I know why you say the things you do. Well, Ill let you confirm that if you want.

Thats not what a durso is for though...you are in fact nullifying its muzzling properties if you are using it to create/boost a siphon/vacuum. You might as well plug the air hole all together. A durso isnt about trying to manipulate the pressures in the standpipe...its just to cover the noise. It should be as if we removed the durso part all together and just left a standpipe (and noise)...thats how a durso should flow...not with a siphon.

 

[kgross]

You state the pipe diameter has something to do with head pressure. You had better check your physics book. This is 100% WRONG. It does not matter if the pipe is 1" or 1' diameter, the head is the same. Head does not depend on volume. Head depends on the height of the water column and barrometric pressure.

Bean you are almost correct here, the only problem is that we are not dealing with static head pressure we are dealing with dynamic, ie with the water in motion. IF the water is not moving at all so there are no frictional head losses you are correct, but since the water is moving there is friction involved. if you have a 1 inch pipe tyring to run full flow though a 1 inch bulkhead you will get a lot less flow than a 2 inch pipe trying to run full flow though the exact same bulkhead. This is simple you can use the reefcentral flow loss calculator to figure this out. You can use any pump with over say 1000 gph, and plug in the numbers the pump will create your head. I don't know if the calculator has a bulkhead in it, but just for the sake of this discussion use a gate valve to pretend it is a bulkhead and see if you get more flow out of 2 inch pipe or 1 inch pipe. The reason is frictional looses, if you have a 1 inch pipe connected to the 1 inch bulkhead, there can be depending on flow enough friction to reduce the functional head pressure (ie dynamic since we are talking flow) to a much lower value than the static head pressure that you keep bringing up. If you use 2 inch pipe you eliminate most of the frictional losses since there lower coeffiant of friction in the 2 inch pipe than the 1 inch pipe, so with the 2 inch pipe any water that builds up above the bulk head does create static and dynamic head pressure against the bulkhead which will be very very close to exactly the same, with 1 inch pipe depending on the flow rate the dynamic head pressure could be much much less than the static so you get much less flow.

Kim

 

[tha_reids]

Looking at this cross section would the flow rate be different on these two setups? Both being 1-1/4" on top and 1" at bottom of tank, reguardless if its plumbed in the interior or exterior.