Pool pressure shows 0 psi on pump "low speed"

[redoctober45]

Hello,

I just realized today that the pool pump (that came with my new house) is a two speed (just turn the switch the other way). However, when I turned the switch to the low speed I get 0 psi on the filter (normally 14 psi on high speed). This is a 75 sqft cartridge system, some 14 year old Jacuzzi pump/filter combo system. The pool is an above ground ~14,000 gal. I mean, on low it feels like it is still working though, just reading no pressure.

What does this mean? Or is this normal?

Thanks for the help

 

[Richard320]

Pretty much normal. You see movement in the skimmer and flow from the returns, right?

You might also try the search box for something like zero pressure variable speed.

 

[svenpup]

Reading zero pressure on low speed is totally normal.

 

[bobodaclown]

Yeap, Normal. Enjoy the savings!

 

[swmrn]

...but the question is, with the "zero pressure" is it actually filtering?
Bought a florida pool house that needed updating so my new Variable speed echostar pump was just installed and set up by the installers. I have a 13k gal pool with a spa. He had it the automation to run at 30% from 6a -3p and then at 90% from 3p-6p for the skimmer and floor popups to work.
Things seemed fine, but then I hired a local chain pool company (pinchapenny) to start up the new salt system and maintain for a while to get things going. The guy came over today, said the salt was fine (but no salt had EVER been added to the pool and the SWG had yet to be turned on because the chlorine level was very high from the previous pool guy). He noticed that the filter pressure gauge was "zero" and implied that it was not filtering anything at that speed and should be turned up.
Who's right?
I tend to think that the water is being circulated/ filtered and exchanged, just at a lower rate, saving electricity.
Im new at this, learning much more that I ever wanted to know about pool maintenance and chemistry. And I have questions. So many questions!
Thanks!

 

[pooldv]

You are correct. The water must go through the filter. My filter shows 0 psi 90% of the time and my pool is perfectly clear. So, it is clearly working. Sorry,

 

[bobodaclown]

Yes, you are correct. Ask away. We're here to help, and our rates are much better. This is one of those cases where you get much more than you pay for.

 

[JamesW]

Pressure varies by the square of the difference ratio. At 1/3 the rpm, the pressure is 1/9th of the pressure at full speed. Also, the typical filter pressure is -2 psi when off.

If the full speed pressure is 16, the 1/3rd speed pressure will be about 0 psi.

As long as the flow switch on the chlorinator stays closed, you're probably good.

If you feel good suction and return flow, you're good.

If we assumed that your system woud be close to equivalent to 200 ft of 2" pvc pipe, a 2 psi pressure (0 gauge) would cause about 35 gpm flow rate.

To determine your filter pressure with the pump off, measure the height of the gauge above the pool surface and divide by -2.31.

 

[Lykly]

My filter shows zero pressure all the way up till the RPMs on my pump get ~2000. In any case, every square drop of water goes through filter.


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