Return Pump Plumbing

Mike T IL · Dec 14, 2020

I have 2 Neptune Apex Cor 20 return pumps, each going to their own turn return into the tank via 1" PVC. Each also feeds a 40w UV. One for Protozoa and one for Algae and bacteria. I am currently getting 580 gph flow rate. For Algea I should have a flow of 950 gph or greater. Here is a picture of my plumbing, are there any changes I can make to increase the flow up to the needed UV requirement?

Brett S · Dec 14, 2020

The pictures are quite small and it’s difficult to follow your plumbing path, but if the pump is at 100% and you’re still not getting the flow you need, then the only options are a bigger pump or reducing head pressure.

Reducing head pressure can be done by trying to simplify the plumbing as much as possible - making the runs as short as possible and trying to reduce the number of 90’s. Or increasing the pipe size. The COR 20 has a 1.25” output and moving from 1” pipe to 1.25” pipe will probably make a significant difference in your flow rate. Finally, you don’t have a picture of the return nozzle in your tank, but if the nozzle is very restrictive that might be reducing your flow rate as well.

Snoopy 67 · Dec 14, 2020

From 580 to 950 is too big a jump for plumbing.
You need the right pump.

Mike T IL · Dec 14, 2020

Brett S said:
The pictures are quite small and it’s difficult to follow your plumbing path, but if the pump is at 100% and you’re still not getting the flow you need, then the only options are a bigger pump or reducing head pressure.

Reducing head pressure can be done by trying to simplify the plumbing as much as possible - making the runs as short as possible and trying to reduce the number of 90’s. Or increasing the pipe size. The COR 20 has a 1.25” output and moving from 1” pipe to 1.25” pipe will probably make a significant difference in your flow rate. Finally, you don’t have a picture of the return nozzle in your tank, but if the nozzle is very restrictive that might be reducing your flow rate as well.

My main interest is the flow going through the UV. I am measuring the pressure via an Apex Flow Monitor right before it enters the tank. I would love to simplify the plumbing. Don't know how I can make any shorter runs.

Mike T IL · Dec 14, 2020

I might get a separate pump for the UV.

Brett S · Dec 14, 2020

Mike T IL said:
My main interest is the flow going through the UV. I am measuring the pressure via an Apex Flow Monitor right before it enters the tank. I would love to simplify the plumbing. Don't know how I can make any shorter runs.

At that point I think your options are a bigger pump and/or upgrading your pipes to 1.25”. However, as @Snoopy 67 said, even with bigger pipes you might have a hard time going from 580GPH to 950GPH just by increasing the pipe size.

Snoopy 67 · Dec 14, 2020

A lower flow rate through the UV will not hurt you in any way you get more contact time.
Unless it affects something else you might not want it to.

Mike T IL · Dec 14, 2020

Snoopy 67 said:
A lower flow rate through the UV will not hurt you in any way you get more contact time.
Unless it affects something else you might not want it to.

Lower flow rate is good for Protozoa but the manufacturer recommend higher flow to fight Algea and Bacteria. My 40w Pentair recommends 157 to 262 gph for Protozoa and 943 to 1574 for algea/bacteria. Hence, why I have 2 UV's, each running on separate return pumps.

DCR · Dec 14, 2020

You would have to increase the piping to 1-1/4" to get 950 gph. Increasing the pump is not really a practical solution and here is why. The COR 20 should be putting up about 14 ft of head at 580 gph according to the flow curve. Assuming about 4 ft of elevation change, that means you have 10 ft of frictional head loss at 580 gph with your current 1" piping. Frictional head loss goes up with the square of the flow, so if you want to increase the flow by 64% to 950 gph, you will have 268% of 10 ft or 26.8 feet of frictional loss - plus the 4 feet of elevation. So a pump that puts up about 31 feet of head at 950 gph would be required.

Head losses really snowball with increasing fluid velocity and the best solution is to increase the pipe diameter.

Having said that, I think the algae control will still be fine at 580 gph. The 950 is a suggested flow, not a minimum and includes ponds. I don't really see the logic that says you need high flow rates for algae control in an aquarium. There is a turnover impact, but I cannot imagine that 580 gph would not be adequate for most any home aquarium. I suspect the suggested 950 gph is more related to a 4700 gallon pond than a 260 gallon aquarium.