GPM vs Water velocity and a variable speed pump


New member
May 20, 2020
Hi Everyone,

Some background:
I have a new house with a new pool. The pool has a Jandy VS pump and the plumbing coming out of the ground is 3" until it converts to 2" when it hits the pump. It converts to 3" just before going back underground. The pool is 25,000 gallons. There is a 36" sand filter and pressures are low. At 1720 rpm the PSI meter is basically 0 and at 2200 rpm it hits about 6 psi. Sand filter is new for this season so I think those are good pressures on a perfectly clean filter.

My question is if I should be concerned with how much "mixing" the return jets provide in the pool. The pump has a Flow meter on it and with it running at 1720 rpm, it is providing 50 GPM and based on my my runtime (18 hours) is more than two full turn-overs. However, at this speed the return jets are pretty low pressure. You can definitely feel it, its just not a powerful jet. The skimmers do have a nice swirling effect so I think they are sucking well.

If I bump the speed up to 2200rpm then I get 90GPM (way more turn-over than 1720) but the jets feel like they are helping to mix up the water better.

So is it better to have the jets providing more exit velocity to mix up the water, or just save some energy and go low and slow? I have not tried swapping out the eyeballs on the jets, they do look really big. Almost like its the full size of the hole. I'm looking at a pool robot in the future but for now using a vaccum head attached to the skimmer to clean the floor (which does not work well at 1720rpm...just doesn't suck hard enough.)

Thoughts? I know turn over rate is a bit of an old idea. Even still, does it matter how slow the water circulates if things are trapped in the skimmer and chlorine levels are good? I have a digital liquid chlorine controller (Hanna BL121) . One thing that gives me pause is that the Hanna controller says to not use CYA, which makes me think chlorine levels could drop if the pump is running more often.
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TFP Expert
LifeTime Supporter
May 3, 2007
Pleasanton, CA
Welcome to forum!

First thing is to forget about turnovers. They have absolutely no bearing on water quality.

As far as mixing the water, twice the run time at half the flow rate will mix the water just as well:

Just run the pump at as low an RPM as possible so that the skimmers still work properly. You can gauge this by water still traveling over the top of the weir door.

As for run time, long enough to skim the surface.

You must have some CYA or you will be using a ton of chlorine.