Overflow Box

jharding08 · 06/25/2012, 08:19 PM

I have always had questions about the correct functionality of my overflow box. I bought the complete LR setup together, 120g glass tank, 30g sump, pumps, plumbing and overflow. I have redone most of the plumbing and moved all the hardware to the end, since I have my tank viewable on 3 sides.

The overflow is a CPR CS100, 10" wide, rated for 800 gph. My return pump is rated at 700 gph, not including head pressure. I got the closed system setup, but the overflow level was really low. The box was missing the screen, vent tube and prefilter sponge that goes on the bulkhead.

Here is the overflow level with just the bulkhead

The problem with this setup is the air that gets in with the suction and makes alot of noise. I started looking into standpipes, but first wanted to try to add an open pipe to recreate what the missing screen and vent tube would offer. I put a 2" piece of PVC in the bulkhead, raising the water level. It is super quiet now, but can the water level be too high in the back reservoir of the overflow? i included a vent tube that is open at the other end. Here is the water level with 2":

It is definitely quieter, but the water level flucuates every once in a while. It will drop very low and start sucking, then come back up and be normal and quiet again. The return flow is constant, so what can cause this? It happens every 20 minutes are so. SHould I look into a standpipe? How tall can I make the standpipe?

One other thing I noticed was that my flow isnt like the video included on the website for the CPR CS100. In the video, the water is flowing over super fast. I have a decent flow, but not that fast. I wanted to calculate my head pressure for my pump and its about 26 ft of plumbing, right angles and back pressure. My return pump again is 700 gph with a 800 gph overflow. Should I be turning over my water 10 times, even if I have two circulation pumps in the tank?

Thanks for your help

poakley723 · 06/26/2012, 09:41 AM

Not sure why you get the syphen effect every twenty minutes but you are probably only flowing 500ghp at the most with your pump. You could probably increase your pump size and that would help the water flow. One problem I always had with the HOB over flow on my 125 is getting air bubbles in the u-tube. I increased the flow and they all went away. More water flow helped to push them through.

About your water fluctuation. is you return pipe in your sump submerged in water. if it is you will have air build up in there and it could cause your surge every 20 minutes.

A stand pipe in that over flow has to keep the water level in the tank side above the level of the side out side your tank. If it is not then your syphen will stop. Just take 2 90's and put them on your tube coming up in your drain area. You should be good with them. make sure you drill a small hole in the top of it to allow air flow. If they are to long to fit in the over flow box just cut them down where they connect at the top to make them fit. As long as water has to flow up and over in the stand pipe it will work all the same.

jharding08 · 06/26/2012, 11:27 AM

What size pump do you recommend I go up to? Should I do a 1000 gph if I'm losing about 200 gph on head pressure?

My return is not submerged in the water, it has a fixture that attaches to the top of the side of the sump and then the water pours in (more noise). I can tell when the water flucuation is going to happen, because the flow rate coming out of the end of the return gets greater and then all the water in the overflow starts to drain until it reaches the top of the pvc drain and then you hear the suction and it starts to refill. I didnt see any issue with the flow from the tank to overflow, must just be air in the return line.

What could be the issue is that the return line (flex tubing) has to enter through a hole cut in the right side of the stand and then travel all the way to the far side of the sump. With the sump being somewhat tall and the hole in the stand almost at the top, the return line does dip before the exit. I can take a picture, but it doesnt flow downhill the whole time. Not sure how I can get it to flow downhill other than with hard plumbing and even at that, it would be a gradual decline.

I am definitely going to try the stand pipe. Is the water supposed to come up just to the inlet of the standpipe or will it cover it?

Agu · 06/26/2012, 01:43 PM

Read up on a Durso standpipe.

There are other styles of standpipes that will accomplish the same thing. A properly designed standpipe will maintain consistent water levels, greatly reduce noise, and eliminate the periodic swoosh of water.

BTW, if you're using flex tubing for your drain line confirm there isn't a low spot where water could be collecting until pressure forces it out.

jharding08 · 06/27/2012, 10:59 AM

Durso standpipe is doing the trick so far. Pretty quiet and good turnover

06/25/2012, 08:19 PM	#1
jharding08 BlueWorldAquatics.com Join Date: May 2012 Location: Murrieta, CA Posts: 657	Overflow Box I have always had questions about the correct functionality of my overflow box. I bought the complete LR setup together, 120g glass tank, 30g sump, pumps, plumbing and overflow. I have redone most of the plumbing and moved all the hardware to the end, since I have my tank viewable on 3 sides. The overflow is a CPR CS100, 10" wide, rated for 800 gph. My return pump is rated at 700 gph, not including head pressure. I got the closed system setup, but the overflow level was really low. The box was missing the screen, vent tube and prefilter sponge that goes on the bulkhead. Here is the overflow level with just the bulkhead The problem with this setup is the air that gets in with the suction and makes alot of noise. I started looking into standpipes, but first wanted to try to add an open pipe to recreate what the missing screen and vent tube would offer. I put a 2" piece of PVC in the bulkhead, raising the water level. It is super quiet now, but can the water level be too high in the back reservoir of the overflow? i included a vent tube that is open at the other end. Here is the water level with 2": It is definitely quieter, but the water level flucuates every once in a while. It will drop very low and start sucking, then come back up and be normal and quiet again. The return flow is constant, so what can cause this? It happens every 20 minutes are so. SHould I look into a standpipe? How tall can I make the standpipe? One other thing I noticed was that my flow isnt like the video included on the website for the CPR CS100. In the video, the water is flowing over super fast. I have a decent flow, but not that fast. I wanted to calculate my head pressure for my pump and its about 26 ft of plumbing, right angles and back pressure. My return pump again is 700 gph with a 800 gph overflow. Should I be turning over my water 10 times, even if I have two circulation pumps in the tank? Thanks for your help

06/26/2012, 01:43 PM	#4
Agu Registered Member Join Date: Oct 1999 Location: Sarasota, Florida Posts: 30,279	Read up on a Durso standpipe. There are other styles of standpipes that will accomplish the same thing. A properly designed standpipe will maintain consistent water levels, greatly reduce noise, and eliminate the periodic swoosh of water. BTW, if you're using flex tubing for your drain line confirm there isn't a low spot where water could be collecting until pressure forces it out. __________________ Less technology , more biology . Current Tank Info: 30 gallon half cube and 5.5, both reef tanks

06/26/2012, 09:41 AM	#2
poakley723 Registered Member Join Date: Dec 2007 Location: San Diego Posts: 128	Not sure why you get the syphen effect every twenty minutes but you are probably only flowing 500ghp at the most with your pump. You could probably increase your pump size and that would help the water flow. One problem I always had with the HOB over flow on my 125 is getting air bubbles in the u-tube. I increased the flow and they all went away. More water flow helped to push them through. About your water fluctuation. is you return pipe in your sump submerged in water. if it is you will have air build up in there and it could cause your surge every 20 minutes. A stand pipe in that over flow has to keep the water level in the tank side above the level of the side out side your tank. If it is not then your syphen will stop. Just take 2 90's and put them on your tube coming up in your drain area. You should be good with them. make sure you drill a small hole in the top of it to allow air flow. If they are to long to fit in the over flow box just cut them down where they connect at the top to make them fit. As long as water has to flow up and over in the stand pipe it will work all the same.

06/26/2012, 11:27 AM	#3
jharding08 BlueWorldAquatics.com Join Date: May 2012 Location: Murrieta, CA Posts: 657	What size pump do you recommend I go up to? Should I do a 1000 gph if I'm losing about 200 gph on head pressure? My return is not submerged in the water, it has a fixture that attaches to the top of the side of the sump and then the water pours in (more noise). I can tell when the water flucuation is going to happen, because the flow rate coming out of the end of the return gets greater and then all the water in the overflow starts to drain until it reaches the top of the pvc drain and then you hear the suction and it starts to refill. I didnt see any issue with the flow from the tank to overflow, must just be air in the return line. What could be the issue is that the return line (flex tubing) has to enter through a hole cut in the right side of the stand and then travel all the way to the far side of the sump. With the sump being somewhat tall and the hole in the stand almost at the top, the return line does dip before the exit. I can take a picture, but it doesnt flow downhill the whole time. Not sure how I can get it to flow downhill other than with hard plumbing and even at that, it would be a gradual decline. I am definitely going to try the stand pipe. Is the water supposed to come up just to the inlet of the standpipe or will it cover it?

06/27/2012, 10:59 AM	#5
jharding08 BlueWorldAquatics.com Join Date: May 2012 Location: Murrieta, CA Posts: 657	Durso standpipe is doing the trick so far. Pretty quiet and good turnover