Slowing pump output bad in the long term?

bla403

New member
Just wanted everyone's thoughts on using a valve to turn down the output of a pump. I have done it before on smaller reactor pumps and have never had any issues but I wanted everyone's thoughts on doing this with larger pumps like return pumps.

What is the point that valving it down too much will hurt the pump in the long term. (ie. turning it down 25% does do much but 50% will decrease the life of the pump a lot)

I have a mag 7 on my 90 gal for a return pump that I run full open but some people have said that I could valve it down to increase contact time in the sump for the skimmer.

I have an avast cs1 pegleg that I just finished buidling (love it btw)
 

Allmost

New member
wouldnt it heat up the pump ?

cause the voltage in is the same ... work is less .... the impeller not turning.
 

Drae

RAIDER NATION!
wouldnt it heat up the pump ?

cause the voltage in is the same ... work is less .... the impeller not turning.

It's just like adding head pressure to the pump. The pump is designed to work with various amounts of head pressure so I'd imagine it would be fine. I had a mag 9 on a 40 breeder once because it was all I had and I must've valued that thing down 60%. It did run a reactor also though but it worked fine and I didn't notice any significant added heat. Just my experience.
 

Allmost

New member
It's just like adding head pressure to the pump. The pump is designed to work with various amounts of head pressure so I'd imagine it would be fine. I had a mag 9 on a 40 breeder once because it was all I had and I must've valued that thing down 60%. It did run a reactor also though but it worked fine and I didn't notice any significant added heat. Just my experience.

okay yea the extra head pressure idea makes sense :) thank you.
 

bla403

New member
yeah head pressure idea does make sense to me. Was just concerned if you valve it down 50% or more if you are causing longer term issues. I wont be doing that it my case but I was curious.
I have done it on reactor pumps but if they die its not the end of the world. No backup for the main pump at the moment which I am going to build something for in the future.
 

ThisGuy12

New member
yeah head pressure idea does make sense to me. Was just concerned if you valve it down 50% or more if you are causing longer term issues. I wont be doing that it my case but I was curious.
I have done it on reactor pumps but if they die its not the end of the world. No backup for the main pump at the moment which I am going to build something for in the future.
Shouldn't be a problem at all. I have mine dialed back to 75%, works fine.
 

Allmost

New member
we should keep in mind that all the "works fine" shared on here are short term, and just looking at it from the outside ....

overworking a pump will lower its life ... and we havent connected them to read the voltage used when head pressure increased ... so u may be wasting energy trying to limit flow ...
 

ca1ore

Grizzled & Cynical
I ran a pump with significant head pressure for almost 20 years, so choking the output really didn't reduce the useful life for me. Downside is that if you choke back a pump it means you are running more pump than you need and burning excess electricity.
 

sirreal63

Go Spurs Go!!!
Premium Member
we should keep in mind that all the "works fine" shared on here are short term, and just looking at it from the outside ....

overworking a pump will lower its life ... and we havent connected them to read the voltage used when head pressure increased ... so u may be wasting energy trying to limit flow ...

The voltage will not change but the wattage will. A typical aquarium pump will use less watts when the output is restricted, as Drae pointed out, it is not any different than adding head to it.
 

sirreal63

Go Spurs Go!!!
Premium Member
I know over the years many people have used a kill-o-watt to measure it. It is no different than running reactors, a chiller or any other output reducing item on the pump. I am not sure if this applies to external pumps like a Reeflo, Little Giant or Iwaki. Other than pumps I have given away that I don't know how long they lasted, I have never had a failed submersible pump but did have to replace a Sedra impeller that swelled after about 5 years.
 

Allmost

New member
Sedra I have had the same ISsue with, I think thats just the Issue with that type.

I guess pressure rated pumps would be different as the impeller cant "skip a turn". but yea all my returns are also restricted a bit, Id say working at 80% maybe.
 

ca1ore

Grizzled & Cynical
A throttled pump drawing less power has something to do with less weight of water to push - or something like that. Completely non-intuitive to me though .....
 

Wazzel

New member
As long as you do not shut it off completely or choke the inlet slowing it will not be an issue. If you choke it down enough to be in the next size smaller pump you should consider changing out the pump to the smaller size. You will be running a bigger pump than you need and wasting electricity.

Pump power is actually a function of pressure and flow. As the pressure goes up the flow goes down. Power tends to rise as the pressure goes up towards the end of the operating curve. It does not matter if it is external or submersible, they function on the same principals. It is the motor that matters on weather or not it can be submerged.

Here is the equation
Horsepower = (Pressure (PSIG) × Flow (GPM))/ 1714

And a typical centrifugal pump curve, which aquarium pumps are.
PumpCurve1-11.jpg
 
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