Return Pump Plumbing - When to reduce down

psumms · Apr 6, 2020

Was thinking last night about most efficient way to plumb a return pump with 40mm output to Red Sea Reefer 25mm return pipe. Looking to minimise running cost and noise from back pressure. So, is it better to run 40mm pipe from the pump up and as far as possible then reduce down or, reduce to the the 25mm straight out of the pump? My initial thought was bigger must be better right? But then got to thinking about the weight of water being 'held' up in the larger pipe vertical climb.

saltyhog · Apr 6, 2020

Great question. I don't think it will matter a great deal as long as the return line from the pump to display is a short one (not running from a basement, etc.) but honestly I don't know which is best. Let's see if we have anyone who is up on the physics of this. #reefsquad

Miller535 · Apr 6, 2020

psumms said:
Was thinking last night about most efficient way to plumb a return pump with 40mm output to Red Sea Reefer 25mm return pipe. Looking to minimise running cost and noise from back pressure. So, is it better to run 40mm pipe from the pump up and as far as possible then reduce down or, reduce to the the 25mm straight out of the pump? My initial thought was bigger must be better right? But then got to thinking about the weight of water being 'held' up in the larger pipe vertical climb.

Many return pump companies recommend bigger, stating it reduces head pressure and produces more flow. So I would say bigger as far as possible.

Miller535 · Apr 6, 2020

Specifically I know Neptune sates this for their Core pumps. I know there are others too, Core is just the one on the top of my head.

JoshH · Apr 6, 2020

Typically it's better to run the wider plumbing for as long as possible and then reduce down. Reducing right from the pump, while doable, will increase the friction loss associated with a smaller pipe. This will more than likely work out to be more restrictive than reducing the pipe at the last point you can...

CK00020 · Apr 6, 2020

bigger is better for less friction loss

ca1ore · Apr 6, 2020

JoshH said:
Typically it's better to run the wider plumbing for as long as possible and then reduce down. Reducing right from the pump, while doable, will increase the friction loss associated with a smaller pipe. This will more than likely work out to be more restrictive than reducing the pipe at the last point you can...

Exactly! I run a basement sump, so my pump has to work against significant pressure …. initially I ran 1" flex PVC from pump to tank and got about 1,450 gph out of my PW250. Then swapped most of the 1" run with 1 1/2" flex (no way to easily change out the final few feet, so that remains 1") and got close to 1,600. Every situation will be different, but larger diameter pipe can help a lot.