I am planning a new set up. I have possible access to a 90 gallon tank with one inch holes drilled in a corner overflow. I am planning on using a Mag 9.5 return pump. The RC calculator suggests that I use a minimum of 1.27" drain pipe diameter to accommodate 950 gph flow. So my question is, what size should the drilled holes be for the drain and return lines? What size bulkhead should I get? Do the drain hole size directly correspond to the bulkhead size? Finally, the RC calculator indicates that the minimum linear overflow size should be at 14 inches. What the heck does that even refer to? Any help would be appreciated.
drainpipe/overflow/bulkhead calulations
- Thread starter drbronx
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jacksonpt
New member
First off, I have a mag 9.5 that I'm not using, if you're interested.
Second, I'm confused - the tank is already drilled with 1" holes, but you're asking how big you should drill the holes? The RC calculators assume a mixed drain (air and water, not full siphon). Based on their recommendation, you should run 1.5" pipes, which would require a 2 3/8" hole (I have a hole saw of this size you're welcome to use if you want). Alternately, you could run 1/2 or 3/4" pipe at full siphon and get most if not all of that 950gph. Those would require 1 1/8" and 1 1/2" holes respectively.
Personally, I'd run a 1" drain at full siphon and a 1" mixed drain (if you have the room for two 1" pipes). This will be mostly fail safe, will be VERY quiet and will require virtually no attention/maintenance. Plus, it can easily handle more flow if you decide to go with a bigger pump at some point. I'm a big advocate of over plumbing for reliability and flexibility.
The amount of flow you want to run, and how you want to run it (mixed or full siphon) dictate what sized pipes you need. The pipes dictate the bulkhead, which dictates the size of the hole.
When they talk about the linear overflow size, they are talking about the linear length of your overflow. My overflow box is 6" wide by 2" deep, so I have 6" + 2" + 2" = 10" of linear overflow. Make sense? This number is a little misleading though, and I can't really explain it in words, but it has to do with how far up the teeth your water level is and how "deep" the water is at the point of overflow... the deeper the water at the point of overflow, the more flow but the poorer the surface skimming.
Second, I'm confused - the tank is already drilled with 1" holes, but you're asking how big you should drill the holes? The RC calculators assume a mixed drain (air and water, not full siphon). Based on their recommendation, you should run 1.5" pipes, which would require a 2 3/8" hole (I have a hole saw of this size you're welcome to use if you want). Alternately, you could run 1/2 or 3/4" pipe at full siphon and get most if not all of that 950gph. Those would require 1 1/8" and 1 1/2" holes respectively.
Personally, I'd run a 1" drain at full siphon and a 1" mixed drain (if you have the room for two 1" pipes). This will be mostly fail safe, will be VERY quiet and will require virtually no attention/maintenance. Plus, it can easily handle more flow if you decide to go with a bigger pump at some point. I'm a big advocate of over plumbing for reliability and flexibility.
The amount of flow you want to run, and how you want to run it (mixed or full siphon) dictate what sized pipes you need. The pipes dictate the bulkhead, which dictates the size of the hole.
When they talk about the linear overflow size, they are talking about the linear length of your overflow. My overflow box is 6" wide by 2" deep, so I have 6" + 2" + 2" = 10" of linear overflow. Make sense? This number is a little misleading though, and I can't really explain it in words, but it has to do with how far up the teeth your water level is and how "deep" the water is at the point of overflow... the deeper the water at the point of overflow, the more flow but the poorer the surface skimming.
jacksonpt
New member
I thought of a way to explain the misleading linear overflow thing...
If you picture water flowing through the teeth and into the overflow, the higher up the teeth the water level is, the more water there is flowing per hour - a very thin stream of water through the teeth flows less water into the overflow than does a deeper stream. Make sense? That is why the rc calc is somewhat misleading on all this.
If you picture water flowing through the teeth and into the overflow, the higher up the teeth the water level is, the more water there is flowing per hour - a very thin stream of water through the teeth flows less water into the overflow than does a deeper stream. Make sense? That is why the rc calc is somewhat misleading on all this.
Thanks professor Jackson for taking the time to offer a very thoughtful and comprehensive explanation of an area that I always found perplexing. I still have a couple of questions about your explanation. What is meant by "full siphon"? Does that mean no air being drawn into the system? How does one determine the siphon mix percentage? And how does thyat determine the pipe diameter requirement? Finally, how does one calculate the size hole relative to a given pipe size (eg. 2 3/8 hole for a 1.5" pipe diameter?)
Any good readings/resources that you found helpful in this area?
Any good readings/resources that you found helpful in this area?
jacksonpt
New member
Most of what I know about this stuff I've learned from reading and reading and reading and reading in the DIY forum.
As for figuring out the hole sizes, I go to glass holes' website and look at the bulkheads they sell. In the bulkhead description they say how big the hole has to be. That's the easiest way I've found, unless you want to memorize all that (I don't, lol).
Full siphon is no air, just water, so there is no such thing as a "siphon mix". The advantage of a full siphon is 2 fold, first: more flow, second: less noise. A regular drain (air/water mix) can be made relatively quiet with standpipes and such, but it's only quiet when flow is reduced to such a point where flow becomes laminar (water flows along the walls of the pipe with air in the middle). Laminar flow requires a surprising little amount of flow through a pipe, which is why standpipes are so popular. Anytime you have air and water mixing, there will be noise.
Now, determining pipe size... I think you're coming at this the wrong way. You can approach the issue from 2 directions... first: What size pipe do I need for XXgph? and second: I've got XX size pipe, how much GPH can I push through it. It sounds like you're trying to use the second approach. I suggest the first. Decide how much turnover you want in your tank. Based on your first post, you're thinking ~1000 gph from the mag9.5, right?
So now figure out how to move 1000gph through your system. A 1" pipe at full siphon will handle that with ease, but a 1" standard drain (air/water mix) will handle ~1/2 of that, and it will be noisy (thus the need for a stand pipe).
I suggest running a 1" pipe at full siphon to handle 80% of your flow. Run a second 1" drain with some sort of standpipe to handle the minimal remaining flow. This will be exceptionally quiet and very reliable.
I'm going to sketch up something for you, may make this all a bit easier to understand.
As for figuring out the hole sizes, I go to glass holes' website and look at the bulkheads they sell. In the bulkhead description they say how big the hole has to be. That's the easiest way I've found, unless you want to memorize all that (I don't, lol).
Full siphon is no air, just water, so there is no such thing as a "siphon mix". The advantage of a full siphon is 2 fold, first: more flow, second: less noise. A regular drain (air/water mix) can be made relatively quiet with standpipes and such, but it's only quiet when flow is reduced to such a point where flow becomes laminar (water flows along the walls of the pipe with air in the middle). Laminar flow requires a surprising little amount of flow through a pipe, which is why standpipes are so popular. Anytime you have air and water mixing, there will be noise.
Now, determining pipe size... I think you're coming at this the wrong way. You can approach the issue from 2 directions... first: What size pipe do I need for XXgph? and second: I've got XX size pipe, how much GPH can I push through it. It sounds like you're trying to use the second approach. I suggest the first. Decide how much turnover you want in your tank. Based on your first post, you're thinking ~1000 gph from the mag9.5, right?
So now figure out how to move 1000gph through your system. A 1" pipe at full siphon will handle that with ease, but a 1" standard drain (air/water mix) will handle ~1/2 of that, and it will be noisy (thus the need for a stand pipe).
I suggest running a 1" pipe at full siphon to handle 80% of your flow. Run a second 1" drain with some sort of standpipe to handle the minimal remaining flow. This will be exceptionally quiet and very reliable.
I'm going to sketch up something for you, may make this all a bit easier to understand.
jacksonpt
New member
OK, have a looksee at this
The short drain will be your full siphon. Use the ball valve on it to dial back the flow so that it is pulling just slightly less than your return is feeding the tank. This will do 2 things... first: it will keep the pipe completely under water, thus not sucking air, thus not making noise. second: it will allow the water level in the overflow to rise (remember, the return is pushing water into the tank faster than the siphon is draining it) which will help prevent water from splashing as it flows over the overflow wall.
As the water rises, it will eventually hit the stand pipe. The standpipe will drain the remaining water return by your return pump. Once you get the siphon dialed in, the stand pipe will see relatively little flow and thus remain very quiet.
On the siphon line, I used a ball valve, but you should probably use a gate valve as it will allow you to fine tune the flow in the line a bit better.
The short drain will be your full siphon. Use the ball valve on it to dial back the flow so that it is pulling just slightly less than your return is feeding the tank. This will do 2 things... first: it will keep the pipe completely under water, thus not sucking air, thus not making noise. second: it will allow the water level in the overflow to rise (remember, the return is pushing water into the tank faster than the siphon is draining it) which will help prevent water from splashing as it flows over the overflow wall.
As the water rises, it will eventually hit the stand pipe. The standpipe will drain the remaining water return by your return pump. Once you get the siphon dialed in, the stand pipe will see relatively little flow and thus remain very quiet.
On the siphon line, I used a ball valve, but you should probably use a gate valve as it will allow you to fine tune the flow in the line a bit better.
Thanx Jackson....a picture is truly worth 1,000 words. This is very helpful.
The 90 gallon tank in question, presently has one 1" hole drilled in the side glass near the bottom corner and their is a rectangular glass overflow from the bottom to the top of the tank as in an AGA aquarium. I could redrill the existing hole and perhaps there is room to drill a second hole. The other option is to utilize that overflow for the full siphon, and perhaps purchase a nano size gl*******s overflow as a partial siphon overflow. Does that make any feasible sense? Perhaps Geo can chime in here since he constructed the overflow in question.
Regardless, I have learned a bunch from these explanations (hopefully others are as well) and for the first time I am starting to comprehend the process. Thanks loads Jackson!!
The 90 gallon tank in question, presently has one 1" hole drilled in the side glass near the bottom corner and their is a rectangular glass overflow from the bottom to the top of the tank as in an AGA aquarium. I could redrill the existing hole and perhaps there is room to drill a second hole. The other option is to utilize that overflow for the full siphon, and perhaps purchase a nano size gl*******s overflow as a partial siphon overflow. Does that make any feasible sense? Perhaps Geo can chime in here since he constructed the overflow in question.
Regardless, I have learned a bunch from these explanations (hopefully others are as well) and for the first time I am starting to comprehend the process. Thanks loads Jackson!!
jacksonpt
New member
First, regarding the glass holes boxes. From what I've read, and somewhat from my short experience with them, they are best when run at either very little or near max flow. If you get a 700gph box and run 400gph through it, it's rather noisy. If you dial it way back to 150gph, it's nice and quiet. I don't know if that's the case for all their boxes or not, but wanted to give you a heads up.
OK, back on topic. If I understand your setup, this probably better reflects what I'm recommending.
The bottom hole is the existing hole, which would work well for the full siphon drain. You'd want to drill a second hole above for your open drain.
What you can't see in that drawing is what's inside the box.
The lower hole really only needs a screen/strainer of some sort to prevent snails and such from getting in there. One caution though - if your overflow box ever leaks (water gets into the box somehow other than over the top), your tank will drain until your water level reaches that lower hole.
The upper hole is similar... really only needing a screen or a strainer. What you might want to consider is using an up turned elbow, almost as a second overflow. This would allow you to really fine tune the water level in the overflow box.
Make sense? I can mock up what the inside of the overflow box would look like, I just didn't have enough room in that drawing as I didn't worry about drawing anything to scale.
OK, back on topic. If I understand your setup, this probably better reflects what I'm recommending.
The bottom hole is the existing hole, which would work well for the full siphon drain. You'd want to drill a second hole above for your open drain.
What you can't see in that drawing is what's inside the box.
The lower hole really only needs a screen/strainer of some sort to prevent snails and such from getting in there. One caution though - if your overflow box ever leaks (water gets into the box somehow other than over the top), your tank will drain until your water level reaches that lower hole.
The upper hole is similar... really only needing a screen or a strainer. What you might want to consider is using an up turned elbow, almost as a second overflow. This would allow you to really fine tune the water level in the overflow box.
Make sense? I can mock up what the inside of the overflow box would look like, I just didn't have enough room in that drawing as I didn't worry about drawing anything to scale.
Blugobi
New member
DB...the overflow in the 90 that your asking about is a custom made "Megaflow" type with 1/4" air hole, which will allow the "mixed siphon"...you gan run a Mag 9.5 with a 3' to4' head at full bore. I can drill you some return holes for bulkheads so you can split the return, add check valves...etc. http://www.fosterandsmithaquatics.com/product/prod_display.cfm?pcatid=12078
The link above will give you an idea of the Megaflow..However the return is not thru the bottom would be in the back top...Im not that good at drilling in Tempered Glass
Geo
The link above will give you an idea of the Megaflow..However the return is not thru the bottom would be in the back top...Im not that good at drilling in Tempered Glass
Geo
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Thanx for the info Geo. Yeah...drilling tempered glass is probably not a great idea. And yes, I probably will need two return holes drilled .
Jackson, again thanks for the great info and illustrations. Gives a lot to consider. Are any othewrs here employing full siphon systems? I'd love to hear from Nate on this.
Jackson, again thanks for the great info and illustrations. Gives a lot to consider. Are any othewrs here employing full siphon systems? I'd love to hear from Nate on this.
jacksonpt
New member
Bean's silent and failsafe overflow thread in the DIY forum is a GREAT read. The things I'm talking about in this thread are based on his design so the principles he discusses apply pretty directly here.
It's a long thread with A TON of info/questions, but it gives more detail (and probably clearer explanations) than I have here.
It's a long thread with A TON of info/questions, but it gives more detail (and probably clearer explanations) than I have here.
jacksonpt
New member
No. You can get away with the hole as is (would be very similar to the glass holes design), but an upturned elbow and a bit of PVC is probably the best bet. If the full siphon drain is tuned properly, the open drain will see so little flow that a stand pipe will not be needed. If you follow bean's design (see my prior post for a link to his thread), the open drain line could become a full siphon if the water level got too high - this would be an additional security measure to prevent flooding.
Google Sketch-up. It's free pseudo-CAD software that can take a while to get the hang of, but is pretty easy to use once you get the feel for it.What are you using to provide those terrific illustrations. You got some kind of autocad software?
jacksonpt
New member
Here is the more complete drawing, showing the inner and outer plumbing.
Siphon Tube: This piece is somewhat optional, but I suggest it as a failsafe. Follow along with me here... Imagine the return pump is off (power outage, feeding, working on the tank, watever)... water will drain to the lowest point. Without this tube in place, water would drain to the lower hole. Not a big deal if your overflow is solid and in good shape - the overflow would drain completely, but the display water level would stay. Now imagine the overflow having a small leak in it - a seam fails, a piece of LR falls again it and cracks it, whatever. Water will then be entering the overflow box as it's supposed to (over the top), but also from the crack. Now when the pump is off, the overflow will drain to the bottom hole (as before), but now water from the display is entering the overflow from the crack, so the water level in the display area will continue to drop until it is below the crack. Now you're staring at a wet floor. Make sense? By using this tube, you raise the lowest drain point, adding one more preventative measure against wet floors. Just make sure it's not so tall that the siphon begins pulling air in with the water (think about one of those little whirlpools that happen when you empty a full sink or bathtub).
So, a lot of explanation, but a pretty basic concept, no?
Open Drain tube: This will control the water level in the overflow. Set this as high or low as you want to keep good surface skimming but without having the water splash as it flows into the overflow box.
Air Line: This is another failsafe, but one that I couldn't draw (I'm not that good with Sketch-up). Basically this is a regular piece of airline tubing that you'll want coming out of the top of the drain line and looping back into the overflow box. Set it so it is just above the open drain tube. What it does is this: If the water level in the overflow box ever rises much above the open drain tube (due to either of the drains being clogged), it will submerge the end of this air line. Doing so will cause the line to temporarily turn into a full siphon drain, allowing MUCH GREATER water flow, and thus compensating for the clogged drain.
Make sense? If not, read bean's explanation - it's much better than what I'm managing to do here.
Open Drain: The open drain will be pulling a mix of air and water. The trick to keeping this quiet is to keep the flow as low as possible.
Siphon Valve: The siphon drain, if left wide open, will pull far more GPH than your return pump will push, so you'll end up with A LOT of gurgling. Use the valve to dial back the flow through this drain. Start with the valve wide open and turn on your pump. Get the water flowing, let it gurgle, then slowly close the valve down. Close it down slowly, in small increments. Stop once you notice the water level in the overflow rising. You want the valve as open as it can be without it pulling air. In effect, this drain will then be flowing ~90% of the GPH you have going through your tank. The remaining 10% will flow through the open drain.
Make sense? I feel like I know this stuff inside out and backwards in my head, but I can't for the life of me type up a decent explanation.
Siphon Tube: This piece is somewhat optional, but I suggest it as a failsafe. Follow along with me here... Imagine the return pump is off (power outage, feeding, working on the tank, watever)... water will drain to the lowest point. Without this tube in place, water would drain to the lower hole. Not a big deal if your overflow is solid and in good shape - the overflow would drain completely, but the display water level would stay. Now imagine the overflow having a small leak in it - a seam fails, a piece of LR falls again it and cracks it, whatever. Water will then be entering the overflow box as it's supposed to (over the top), but also from the crack. Now when the pump is off, the overflow will drain to the bottom hole (as before), but now water from the display is entering the overflow from the crack, so the water level in the display area will continue to drop until it is below the crack. Now you're staring at a wet floor. Make sense? By using this tube, you raise the lowest drain point, adding one more preventative measure against wet floors. Just make sure it's not so tall that the siphon begins pulling air in with the water (think about one of those little whirlpools that happen when you empty a full sink or bathtub).
So, a lot of explanation, but a pretty basic concept, no?
Open Drain tube: This will control the water level in the overflow. Set this as high or low as you want to keep good surface skimming but without having the water splash as it flows into the overflow box.
Air Line: This is another failsafe, but one that I couldn't draw (I'm not that good with Sketch-up). Basically this is a regular piece of airline tubing that you'll want coming out of the top of the drain line and looping back into the overflow box. Set it so it is just above the open drain tube. What it does is this: If the water level in the overflow box ever rises much above the open drain tube (due to either of the drains being clogged), it will submerge the end of this air line. Doing so will cause the line to temporarily turn into a full siphon drain, allowing MUCH GREATER water flow, and thus compensating for the clogged drain.
Make sense? If not, read bean's explanation - it's much better than what I'm managing to do here.
Open Drain: The open drain will be pulling a mix of air and water. The trick to keeping this quiet is to keep the flow as low as possible.
Siphon Valve: The siphon drain, if left wide open, will pull far more GPH than your return pump will push, so you'll end up with A LOT of gurgling. Use the valve to dial back the flow through this drain. Start with the valve wide open and turn on your pump. Get the water flowing, let it gurgle, then slowly close the valve down. Close it down slowly, in small increments. Stop once you notice the water level in the overflow rising. You want the valve as open as it can be without it pulling air. In effect, this drain will then be flowing ~90% of the GPH you have going through your tank. The remaining 10% will flow through the open drain.
Make sense? I feel like I know this stuff inside out and backwards in my head, but I can't for the life of me type up a decent explanation.
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After all your effort, how can I not attempt this configuration. It appears that there should be sufficient space within the overflow, especially given that no durso is required. OK so going with 1" pipes each for the mixed and full siphons, what size holes do I need and bulkheads? The existing 1" hole for the full siphon can be expanded (assuming Geo or you have the necessary bit sizes). What needs to be considered for the position of the top (partial siphon) hole.
Any suggestions for the returns (e.g. size, position etc.) Geo stated he can drill two holes on the back glass so that I can split the return into two return spouts or I can go over the top as well.
Any suggestions for the returns (e.g. size, position etc.) Geo stated he can drill two holes on the back glass so that I can split the return into two return spouts or I can go over the top as well.
jacksonpt
New member
A 1" pipe needs a 1" bulkhead. Most 1" bulkheads use a 1 3/4" hole.
The position of the upper hole doesn't matter too much - just make sure the plumbing from the bottom drain line isn't in the way of the plumbing from the top line. Also, make sure the top of the open air tube (in the pic above) is BELOW the lowest part of the teeth in your overflow to allow proper surface skimming. It's easy to use a longer open air tube to raise the drain level, but once that hole is drilled you can't really lower it.
Position of the returns is largely personal preference. Keep them high as they will drain the tank when the pump is off, but other than that you're really just looking for good flow through the tank and no dead spots (I'm sure know this already).
It's a 90g tank, right? Is that a 4' or 6' tank?
The position of the upper hole doesn't matter too much - just make sure the plumbing from the bottom drain line isn't in the way of the plumbing from the top line. Also, make sure the top of the open air tube (in the pic above) is BELOW the lowest part of the teeth in your overflow to allow proper surface skimming. It's easy to use a longer open air tube to raise the drain level, but once that hole is drilled you can't really lower it.
Position of the returns is largely personal preference. Keep them high as they will drain the tank when the pump is off, but other than that you're really just looking for good flow through the tank and no dead spots (I'm sure know this already).
It's a 90g tank, right? Is that a 4' or 6' tank?
reefscape15
New member
Sorry to but in, but Jackson, do you still have that overflow for sale? After some consideration and research, I'd like to try yours out and see how it works.
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