Do I have a suction leak?

[MostlyCanuck]

Hi folks - hope all are well. Just reopening season here and wondering if I'm dealing with section-side leak.

I always run my VS pump low and slow, 24/7 (25GPM, kicking up to the 40s when there's a heat call). At that low speed, I always had plenty of air bubbles in the pump basket/under lid. However, last season at that same low speed, my cartridge filter registered about 10PSI.

Now my filter pressure is only 3-4PSI when the pump runs at 25GPM, and goes as high as 15-20PSI when the pump rumps up to 65PSI for a high-speed quick skim. This 3-4PSI at normal, low speed is the reason why I ask if I do have a leak... everything otherwise works well, good circulation, skimming, no outcome to complain of.. I just don't get what could have caused filter pressure to drop that much.

I of course cleaned skimmer and pump baskets, tightened and lubed suction side unions at the pump + pump lid to ensure the low pressure wasn't due to that.

I also used both a drain king (drain bladder) and a cyclone blower to dislodge any potential blockage in the suction pipe, and...:

1) inserting the bladder into the pump suction pipe, literally nothing comes out of the skimmer end - which makes me think bladder is pushing water out from underground leak? (I thought this would result in water being forced out visibly from skimmer just like when blowing lines)
2) inserting blower into the pump suction pipe, water bubbles out of skimmer (though perhaps not as strongly as should)
3) inserting blower into the skimmer suction pipe, there seems to be way more resistance and I can't keep vac hose into skimmer hole for more t
han a couple seconds... which makes me think maybe there is an obstruction close to skimmer end

So, I am not sure if I have a leak, an obstruction, or nothing at all (and maybe for my pool it is indeed normal to only have 3PSI with a clean filter and low-speed circulation at 25GPM).

What do you think is going on re leak vs no leak? And if pool works well, are there any problems with very low filter pressure anyway?
Thx!!!

 

[Texas Splash]

I'm leaning more towards a blockage. Do you also have a drain? If so, does it have its own line to the pad so you can compare water pull and pressure at the filter? You're not losing prime to the pump are you? Pump pot always full? When the system is turned off, do you lose water?

 

[MostlyCanuck]

drain is plumbed to skimmer, not independently to pump.
pump never loses prime and water always in - though as mentioned there's always lots of air in pump at all times (at low speed like 25GPM half pump basket is air generally, while at higher speed like 40-60GPM basket is full albeit with a few air bubbles).

should I even care about this very low pressure as long as all circulates and filters fine? doesn't seem to impact outcomes...

 

[Texas Splash]

should I even care about this very low pressure as long as all circulates and filters fine? doesn't seem to impact outcomes...

As long as the pump pot is mostly full you should be okay. VSPs often need an rpm increase once or twice a day to purge air. Looks like you've already checked all the regular suction side suspects. Of course the filter PSI will always be lower when your pump is at a low rpm. This may be one of those issues where it's just something to monitor for a while. As long as the pump is happy with the supply of water you're okay.

 

[MostlyCanuck]

thx Pat - as you were typing this I read the thread below where, while rather old, most seem to suggest that near-zero PSI readings on a filter are perfectly fine with a VSP. that's positive and aligned with your comment..

Pool pressure shows 0 psi on pump "low speed"

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...

www.troublefreepool.com

in my case though something more is obviously going on since readings were stable at 10PSI for a whole season and now suddenly dropped to 3PSI, which is why I also suspect a blockage maybe.. just not sure how to validate the concern (or unblock it) if the drain bladder wasn't enough to dislodge it.