Return Pump

[dylema]

I am planning a sump to add to my 20g tank. I know that the pumps claimed flow rate will be reduced because of the water having to be pushed up into the main tank. Is there a way I can work out how reduced the flow will be? The pump will be only about 1m below the water level in the main tank. Will I need a 2000 Lt/Hr to get a rate of 1000 Lt/Hr?
Thanks in advance.

 

[Matthew5664]

It will also depend on the size of the pipe comming from the main tank to the sump.

What size are you using?

The best way to do it is run a T with a ball valve of some sort, back into the sump and alterthe frlow until its balanced.

I use 34 mm from tank to sump. 20mm with a 1000l/h pump back to the tank with a head hight of 1m and the T back to the sump has a about 20l/h through it

hope that helps in some way

 

[dylema]

Yes That does help thanks. I am not sure about what size I will be using yet. From main tank to sump I was thinking of 25mm because that seems to be a standard size for a bulkhead attachment. Is this likely to be too small? I have to decide on my overflow too. I think I will probably make or get made a custom one because the only overflow boxes I can find seem really expensive for what they are. The T and ball valve is a good idea because then I can slow down the flow without overloading the pump.

Still wondering though about the reduced flow due to gravity. No use buying a huge pump only to send half the water back into the sump if I can avoid it.

 

[Matthew5664]

I think that 25mm is to small unless your going to have two of them, one in each corner. you will find the head loss for pumps in the instructions.

Basic plumbing help try this site for more help

 

[SkiFletch]

I disagree, 25mm should be more than wide enough for a low-flow application like that. The general rule of thumb is to use tubing that has nearly an identical (or slightly wider) inner diameter to that of the outlet fitting of the pump. So if your pump outlet is around 20mm ID, use 25mm tubing. If its a 30mm ID, use 34mm tubing. Depends a lot on the pump in use.

 

[andywg]

25mm is more than enough for 1000lph. I run around a 2000lph pump (eheim 1060) though 25mm plumbing and it has no problems at all.

If you are worried about reduced flow from gravity, look for a head chart. Most pumps will show how the flow rate decreases with head height to allow you some idea of the loss. There is also frictional loss, but that won't be too great in a situation such as this (unless you have an inordinate amount of bends in your pipework).

 

[dylema]

Thanks everyone. The return pipe will only have to have a slight S shape and probably a smooth U over the tank edge not sharp bends so I guess friction is not a big issue. I might wait until I have decided on the pump before I decide on diameter for overflow piping. I currently have 500lph running through 12mm hose that is standard for my canister so I guess 20-25mm would be enough for 1000lph. Thanks for that link Matthew there is lots of detail there. I am looking at a 1400lph that I can get cheap I think that will be the goer, should be enough to get 1000lph over the top fingers crossed.