Sump noise

[WestTexasReefer]

I replaced my sump this weekend and changed some of my plumbing. It is a RR 180 with overflow on each end and 2 holes in each overflow for 1" bulkheads and Durso standpipes. I am running 2 Sicce 3.0 return pumps dialed back (redundancy) at the same flow rate as before and the short return is just silicone tubing to ball valve to tubing to bulkhead just like before. On the longer return run I mounted 3/4" hard PVC to back of stand and then connected to pump and at bulkhead with silicone tubing in stead of silicone tubing the entire distance. I changed my drain lines from the ribbed pool hose to 1" spa flex PVC which is glued to the bulkhead drops down and is glued into an elbow on sump and glued to a bulkhead with hard PVC glued into the bottom of the bulkhead where it empties into sump below water level at the same distance as previous sump. Before the change it was silent now I am getting a loud burping of air bubbling up in the sump on the short side drop every minute or so. The longer run doesn't do this and is quiet. Any ideas on how to fix this issue? More flow? Less flow? Make some type of adjustment on Durso? Replace Durso with some other type standpipe? Tank is up and running so drilling holes etc is not an option. Plus I really suck at plumbing. What would be the easiest way to fix?
Thanks in advance.

 

[uncleof6]

The flow rate through the shorter run is too high, hitting a fairly hard coded limit for durso standpipes (it is air locking/purging; pipe more than 1/4 full of water) a testement to the fact that dual overflows don't work as expected, as two drains (even if they are configured the same) will not flow the same. With the longer run, the flow rate is within the limit. But even adding two sicce 3.0 pumps together full open, (rather than dialed back,) is still less than what this tank should be flowing which is in the neighborhood of 1800 gph. Both the drains at this point would be choking beyond imagination. I guess (by drain performance) your flow rate is down ~ a couple hundred gph if that. Some of this due to extreme friction loss in the 3/4" return line, as well as having the small pumps dialed back. The return line should be 1" from the pump outlet to the return outlet in the tank.

The smallest practical durso type standpipe is 1.25" on a 1" bulkhead (from the inventor,) but this hardly gives good performance for large tanks. The upper limit for 1.5" (including bulkhead) is ~ 350 gph, still unsatisfactory for large tanks (even with two of them.) A rough estimate at best, but the hard limit is the pipe being 1/4 full of water.

Any system where the flow rate needs to exceed these limits, should be running a siphon system. At a minimum, a siphon and dry emergency for each overflow, and keep the dry emergency dry, not with a 'trickle' of water through it, which short circuits the fail safety of the system. With a dual discreet siphon system, the natural imbalance between the two siphons is mitigated by discreet adjustment (a valve on each siphon.)

On the two pumps: Two pumps running continuously, carrying ~the same work load, for the same amount of time—are likely to fail ~the same time, and is not a redundancy system. A fail safe is two pumps with one NOT running, and only put in service if/when the first pump fails.

You have two possibilites: lower the flow rate more (a bad idea since you are light flow wise to begin with) or break it down and try again using the fluid dynamics to your advantage rather than against you.

 

[WestTexasReefer]

What do you mean by using fluid dynamics to my advantage?

 

[planedoc]

Usually when that happens you need more airflow in the top of your durso. I don't know if you drilled holes in the top or have a valve but it needs a little more air. Open the valve or drill another small hole or make the existing hole bigger. A 180 needs about 700 to 1200 gph. (4-6 times tank volume). Drilling more small holes is best because they can be easily plugged if needed. A valve is even better because over time durso drains need adjusted to keep quite. Like said above if you really want 10 x tank volume flow you will need to upgrade to a herbie style overflow system, it's not necessary but it is an upgrade

 

[uncleof6]

What do you mean by using fluid dynamics to my advantage?

Fluid Dynamics: The physics that govern how water transporting piping systems work. Right now they are working against you (the hard limits for durso standpipes for example; extreme friction loss in your return lines for another example.) Working for you: Siphon systems are silent, and have far larger flow capacities (operating range/bandwidth,) and have different operating characteristics. An increase in pipe diameter, even just 1 standard size, decreases friction loss by 2/3 - 3/4. Perhaps 'to your advantage' is a bit misleading, and 'knowing the limitations due to the physics' is a bit more clear, and using methods in which the physics will not prevent you from getting where you need to go.

 

[uncleof6]

Usually when that happens you need more airflow in the top of your durso. I don't know if you drilled holes in the top or have a valve but it needs a little more air. Open the valve or drill another small hole or make the existing hole bigger. A 180 needs about 700 to 1200 gph. (4-6 times tank volume). Drilling more small holes is best because they can be easily plugged if needed. A valve is even better because over time durso drains need adjusted to keep quite. Like said above if you really want 10 x tank volume flow you will need to upgrade to a herbie style overflow system, it's not necessary but it is an upgrade

In short no. The more air you have in the pipe, the less water can be in the pipe. The result is: the laminar flow rate decreases with an increasing amount of air in the pipe. Exactly opposite of the common advice. You can't cheat the physics.

Let's take a closer look:

An open channel works when water clings to the wall of the pipe with calm (not moving) air in the middle. This is called laminar flow. There should be no airflow into the standpipe, rather still calm air. When there is airflow into the stand pipe, the flow becomes turbulent, the air and water mix...

What determines the function of an open channel drain, is the amount of water in the pipe, not the amount of air. (though the less air, the higher the flow capacity, till there is no air in the pipe and it operates at siphon, and the more air, the less water...) once the pipe is 1/4 full of water, the flow changes from laminar flow to turbulent flow. The symptoms run from mild, to toilet flusing depending on how much above 1/4 full you go. They can be tweaked by reducing the amount of air, thus increasing the flow capacity, but the closer you get to siphon, the more unstable the drain is, and it will never be silent. You can't beat the physics.

 

[WestTexasReefer]

With the set up I have and limited plumbing skills how would I break it down and try again? I have screened top and don't want to bring returns over the top plus getting behind the tank would require breaking down sump and removing plus still not sure there is room since tank is close to wall. The issue is just with one side and the run from bulkhead to drain is maybe 2 feet. Lower flow or is there a simple fix to one drain?

 

[planedoc]

I'm just stating the fact that until a durso is maxed out increasing the air flow will prevent it from going to siphon. And that is what it's doing. Since its only doing it every minute or so I'm betting a little bit more air will fix the problem. It won't hurt to try by adding another hole or opening the valve a little more. I run dursos on both my tanks. If I put my finger over the air inlet it goes in siphon mode. It will let water build up until it goes into a full siphon once the overflow is drained it sucks air gurgles and the process starts over. Fact is with fine tunning you can get very close to a full siphon with a durso. Problem is that it hard to maintain that perfect balance. That is why a herbie is so much better as the second drain acts like a buffer and let's the main drain keep its full siphon perfectly. It is by far a better system.

 

[uncleof6]

You will have to lower the flow rate in the tank overall, the only solution that won't need plumbing skills. Or increase the pipe size on that side, and cross your fingers. (The 1" bulkhead is a limiting factor here.) While you are at it, increase the pipe size over all.

It is spilt milk at this point perhaps, but there is a lesson to be learned here. Get the plumbing right the first time, not the second or third try...there are thousands of words of good information on drain systems here, unfortunately the not so good information comes up more often

 

[uncleof6]

I'm just stating the fact that until a durso is maxed out increasing the air flow will prevent it from going to siphon.

Even maxed out, it will not go to siphon, it can't; it will certainly not be stable or silent.

And that is what it's doing. Since its only doing it every minute or so I'm betting a little bit more air will fix the problem. It won't hurt to try by adding another hole or opening the valve a little more. I run dursos on both my tanks.

No, it is not going to siphon, it cannot, it is trapping air due to turbulence in the drain line. As long as the stand pipe is not air tight it will never go to siphon. I spent years fighting with dursos, and because there is no fix for them other than low flow rates, there is a concerted search for better drain systems, if they could be made to work at higher flow rates, no one would be looking for a better solution.

If I put my finger over the air inlet it goes in siphon mode. It will let water build up until it goes into a full siphon once the overflow is drained it sucks air gurgles and the process starts over.

Of course it will. NO air = siphon, air = open channel.

Fact is with fine tunning you can get very close to a full siphon with a durso. Problem is that it hard to maintain that perfect balance.

Yes with fine tuning you can get close to siphon operation, but it is not going to be stable, and it will not be silent. Thank you for endorsing the facts. Unfortunately an open channel adjusted in this manner is not safe either. A plug in such a set up is a flood period.

That is why a herbie is so much better as the second drain acts like a buffer and let's the main drain keep its full siphon perfectly. It is by far a better system.

In short no. The 'Herbie' modification does not include a buffer for balancing the system. Modifying the 'herbie' to include a buffer, is every bit as unsafe as tweaking a durso to near siphon. The 'herbie' is comprised of an open channel, and a DRY emergency. In line with the conventional wisdom: never run a siphon without a DRY emergency back up. A DRY emergency is dry e.g. it does not have water in it during normal operation, and should only flow water in the event of a siphon blockage. A pipe with water running in it, is a plug risk. That is the way it is. Those that champion the improper implementation of the 'herbie' are showing careless disregard for the safety rules concerning siphon systems, that existed long before many of them entered the hobby.

The herbie is only 'better' in that it fits in a corner overflow—the very specific intent of it; siphon systems were in use long before herbie published his thread. Flow capacity, and silence, are the advantages; they are not 100% stable, though a siphon system will 'self adjust' to an extent with no help (change in head height.) The bandwidth is rather narrow however. That is it.

Bean's system covers all three issues with drain systems: flow capacity, silence, and self adjustment (stability.) Bean is not careless, and neither am I: all three pipes must be used. Unfortunately, Bean's system is not well suited to dual overflows, or corner overflows in general for that matter.

 

[planedoc]

I'm a definitely more educated in fluid dynamics than I was yesterday but I still bet another hole in that gurgling durso will fix the problem.

 

[WestTexasReefer]

The Durso is the mega flow which you can adjust the stand flow height to whatever level you want in the overflow with a per drilled hole in top. When you say drill another hole do you mean make the one in top larger or drill holes in the pipe going into sump to release trapped air before it goes underwater? Wouldn't a bigger hole in top pull more air in?

 

[uncleof6]

I'm a definitely more educated in fluid dynamics than I was yesterday but I still bet another hole in that gurgling durso will fix the problem.

Sorry, since you cannot beat the physics, it will not fix the problem. It may mask it, but ultimately the flow rate is going to be reduced. The problem is caused by the amount of water in the pipe, not the amount of air.

 

[uncleof6]

The Durso is the mega flow which you can adjust the stand flow height to whatever level you want in the overflow with a per drilled hole in top. When you say drill another hole do you mean make the one in top larger or drill holes in the pipe going into sump to release trapped air before it goes underwater? Wouldn't a bigger hole in top pull more air in?

Yes a larger hole will pull in more air. The only way to stop it from 'pulling in air' which you don't want the stand pipe doing, is to reduce the flow rate, till the pipe is <= 1/4 full of water.

The basics of a durso, is that it is a low flow device. It has a set operating range, based on pipe size and bulkhead size (same as any drain siphon or otherwise.) Unfortunately the inventor, Richard Durso, did not understand the physics of how his stand pipe really works, (by his own admisson.) The resulting invention solved the original issue (eliminate the waterfall in the overflow) but it did not address flow rate differences between freshwater and saltwater; nor does it address flow rates for multipass systems (which marine systems are.) Freshwater are multipass as well, but are far more tolerant of low flow rates. Quite honestly in aquarium evolution, the durso should have been passed by in favor of siphon systems. The only reason the durso wasn't passed over, is that requirement for a dry emergency.

 

[WestTexasReefer]

Would there be a way to release air from the PVC after it goes into the sump but before it reaches the sump waterline? Just thinking out loud that if some of the air were released I would just have micro bubbles coming out the end instead of the pipe burping which is the way it was before making this change. Maybe a T at the waterline partially submerged? But then would I hear running water? How many gph should I be pushing thru this system, 900 would be 5x. The Sicce are rated at 714 each before head loss. One goes straight up about 54 " the other goes up a 24" then 5 foot vertical and then up about 30" so I am not sure what the head loss would be and what the pumps are actually pushing.

 

[uncleof6]

Yeah there are some quick fixes along those lines, but they don't solve the problem, and always involve lowering the flow rate, which is why the band aid seems to work. The confusion comes in with 'guessing' what the flow rate is, when in fact the flow rate is often much less than 'guessed' at. With your system some would guess it to be a 1400gph, failing to take into account the total dynamic head loss. Some would guess it without taking into account the friction loss. It isn't as simple as looking at a flow curve, and picking a number, and the pump rating is for a pump with 0' head pressure, and no pipe.

As far as flow rate goes, it is a tough row to hoe, to make 100% convincing arguments for any particular arbitrary 'rule of thumb.' The rules of thumb that have been the norm, have been in existance for 40 years, but were not created for the type of systems run today, rather for undergravel filters, which if one is willing to do the work, will run a reef tank. One of the more successful startup methods for reef tanks involves an undergravel filter, air driven. Though the 'rule of thumb' said 3 - 5x, these systems always did better at higher flow rates, if one acutally took the chance to bump up the flow rate.

Of course it is never quit that simple, and the function of power heads enters the equation, and what the intended purpose of them is, which has evolved from providing vertical mixing, to somehow adding to the recirculative flow rate, which is a bit questionable since the two do different things, all the way to making up for the lack of main pump flow so you don't have to use such a big pump. It can get to be a bitter debate. Common thought/practice vs. logic. What is clear is rules of thumb are arbitrary, and my 10x + is arbitrary.

What can de determined is that in a single pass system, low flow is going to win, hands down. In a multipass system, the higher the flow rate, the more effective the processing, as it were. Surface skimming/surface renewal is far more effective at higher flow rates, gas exchange is improved (improved surface renewal,) quick surface skimming, keeps the effluent from the tank richer in dissolved organics, becasue not as many are mixed back down into the tank, and this improves the skimmer performance as it is based on the concentration of organics in the influent.

This is not a simple topic, and rules of thumb don't even scratch the surface of it, and actually ignore the 'multipass' functioning system that is an aquarium. But it is fairly simple logic.

 

[SGT_York]

Using two herbie's one in each overflow is a great solution that is easily done. Use the smaller hole for the siphons, and close off both siphons completely when you first turn on the pump, that ensure's your dry emergency can handle the flow and it is easier to set, there is a balance between the two siphons so stop adjusting the first after the water in the display is higher than the water in the first overflow. It takes a bit of patienct to set both herbies. Once they are set they are good, if you are constantly tweaking them something is wrong.

A bean animal is certainly a better setup but with a reef ready tank that is running a herbie is a great viable option that is very easy to get going.

If a durso is "pulling" air that means the siphon is already started and you have too much flow. for a durso to work quietly it needs an entire undisturbed column of air in the pipe if that air column is blocked even for a moment you get the slurping gurgling sound as the water and air mix in the pipe.

Also make sure you have some sort of screen or protection device as all siphon systems are snail magnets, I prefer a lid on my RR overflow which keeps both algae and livestock out of the siphon.

 

[planedoc]

Where the water enters my sump I run a pipe straight up with a 180 (2 90's) too like you said let the air escape. I have found it works great. Here are a couple pics one of the filter area and one of refuguim. The electrical tape holds in filter foam that keeps the noise down even more. One drain drains to filter sock chamber and the other is plumbed to both with a valve in fuge to control flow.

 

[planedoc]

The Durso is the mega flow which you can adjust the stand flow height to whatever level you want in the overflow with a per drilled hole in top. When you say drill another hole do you mean make the one in top larger or drill holes in the pipe going into sump to release trapped air before it goes underwater? Wouldn't a bigger hole in top pull more air in?

I'm saying drill another hole in the top. It's easier to drill additional small holes in the top rather than making the hole you have larger because you can easily plug a small hole to correct if you go too far. I thought I explained that earlier but maybe no clear enough. Ultimately it best to have a valve on top because dursos need adjusted from time to time.

 

[uncleof6]

I'm saying drill another hole in the top. It's easier to drill additional small holes in the top rather than making the hole you have larger because you can easily plug a small hole to correct if you go too far. I thought I explained that earlier but maybe no clear enough. Ultimately it best to have a valve on top because dursos need adjusted from time to time.

In short, no.

Getting to the meat:

Richard Durso, suggested varying the size of the air inlet hole, as a means to 'tune' a Durso standpipe. I do understand the physics involved, and how it works. However, (with all due respect to Richard Durso) in his own words he stated he did not understand the physics at work with his design. He just happened to stumble on something that worked for him in solving a very specific problem: to reduce the height of the waterfall, into the overflow. The introduction of air into the standpipe was to prevent it from running at siphon.

The bottom line is that 'air assisted' standpipes (Durso, Stockman, Glass-Holes, Hoffer Gurgle Buster, DIY PVC overflows, Slit-pipe overflows, and numerous other modifications of the same theme, differing only in where or how the air is introduced) depened on the balance of several variables. This balance only occurs within a rather narrow range of flow rates. The range extends from just a trickle flowing to a point where the pipe is 1/4 full of water. At this point, the flow changes from the 'laminar flow' typical if the balance is right, to turbulent flow. The air and water mix. Flowing out of range, the symptoms will be instability, noise, and injecting large amounts of air bubbles into the sump. The degree of the symptoms depends on how far out of range the flow is. An air assisted standpipe running out of range, will suck in air, seemly indicating that the standpipe needs more air. So of course, letting more air in will fix it. Although increasing the amount of air in the standpipe, is the answer, enlarging the hole (or using multiple holes) is not the answer.

We know (or should) that laminar flow depends on the balance between water and air. This balance reaches its upper limit when the pipe is 1/4 full of water. (1/4 water, 3/4 air.) If the air flow is used as the 'control', this is where it goes:

Let's say, the pipe is 1/2 full of water, and out of range. (obviously.) Using the air flow as a governor, we enlarge the hole to allow more air in. Since the pipe is 1/2 full of water, and 1/2 full of air, where is the additional air going to go, and what is it really going to do. It is going to go straight through the standpipe, mix with the water, be ejected as bubbles, and you need a contraption at the bottom so the air can escape before entering the sump. This is pretty far from working great. Since there is only a finite volume in the standpipe, you cannot increase the volume of air in the standpipe, unless you reduce the volume of water in the standpipe, till the balance is achieved (@ 1/4, or less, full of water, 3/4 full of air.) So absolutely nothing has been accomplished. From this it can be logically deduced that the more air in the pipe, the less water can be in the pipe. (Finite volume.)

On the other hand, we take the same out of range standpipe, and decrease the amount of air in the pipe, since there is a finite volume, it can be deduced that the less air in the pipe, the more water can be in the pipe.

It is obvious, from the above, that most have this exactly and specifically backwards.

This can easily be observed in actual practice. From a trickle to the pipe being 1/4 full of water, they behave well, are stable, quiet, and bubble free. With no air in the standpipe, (siphon) we have a stable, absolutely silent, bubble free drain. In between, a silent and bubble free system cannot be achieved without jumping through hoops and gadgets that merly mask some of the symptoms, but do not come close to solving the problem, and they will not be stable. The closer the standpipe comes to siphon, the more unstable it becomes, and they will never be completely silent. It is a compromise somewhere between turbulent flow and siphon; between ideal and what an individual is willing to put up with. No way to run an airline...(pun intended.)

I stated earlier, that more air in the standpipe is the answer. It begs the question of how to do that, and maintain the balance. Pretty simple actually: increase the pipe size. The other solution, since the 'air flow' is not the control for the standpipe, is to reduce the flow rate. Those are the only two solutions to the problem, you can't beat the physics.

In the end, if you are running ~350gph or less (approx.) a durso will be suitable in just about every case, if it is sufficient in size (1.5".) If flowing more than ~350gph, serious consideration needs to be given to running a siphon system, as you are going to have problems with an air assisted drain. It becomes a question of what the individual is willing to tolerate.