Should I install a valve before this pump (picture)?

ol_whistle_britches said:

I don’t worry about this. I believe the air relief valve at the top of my pentair DE is actually supposed to be somewhat self burping in normal use. I don’t remember if I read that in the manual, or if that’s just how mine ran before I rebuilt it.

You said previously you’ve been running the pump this way for months and never had an issue with it losing prime completely. At this point, I’d say you’re good. Sounds like a quirk. Even if you did have a suction side leak, based on what you’re seeing, I’d monitor and live with it.

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I'm pretty sure my old Pentair 2000 series air valve is manual only. It has previously accumulated a LOT of air until I purge it manually. In last few days (after cleaning basket on 4/20/25 and deep cleaning the filter grids on 4/24/25) I have not had a lot of air in the filter, but then the pump has either not been ON or it has been run continuously with only one priming event to start with.

PoolStored said:

When was the last time you cleaned the filter?
Have you done an OCLT lately? Do one tonight...Link-->Overnight Chlorine Loss Test
A pump not being able to vacate air is indicative of a dirty filter, that may or may not be caused by algae.

You pump should be able to clear the air. With a suction side leak, or air coming in at low speed should happen after the pump fills.

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•Filter was disassembled, cleaned (one grid with a worn spot was also replaced) and reassembled on 4/24/25. It was very dirty, but strangely the pressure readings were not high. They were only about 27 PSI, which is about the same after a complete cleaning (26 psi).

•I haven't done an OCLT lately, but the pool water is crystal clear and I keep chlorine levels up. I can try the OCLT test tonight for good measure.

•The pool was replastered last November, and I haven't had any algae since refilling.

•The pool did accumulate some debris since the replastering and was removed by manual brush vacuuming to the filter. Admittedly, I was not good about cleaning the basket and filter until this month (I did keep the skimmer basket clean though). Both the pump basket and filter grids were very dirty. But both have been very clean since 4/24/25, and I still have a large air "bubble" in pump basket area -- it's really too large to be called a bubble, since the water level does not touch the dome of the clear lid, but almost reaches it.

HermanTX said:

This is a single line leading to your pump. Is this coming from a single skimmer or 2 skimmers?
Ensure that your skimmer baskets are not filled with debris. Don’t make your pump work harder than it has to.

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Yes, it is a single line leading to the pump from my single skimmer. The main drain connects to this line just below the skimmer, so both water sources travel to the pump though the single 1.5" copper pipe underground. There is a plastic diverter thingy inserted in the pipe at the bottom of the skimmer that directs either main drain or skimmer water (or a mixture of both) to the pump by manually turning this plastic diverter

PoolStored said:

1. There is some impediment like leaves in a skimmer or stone in the line.
2. The OP has a dirty filter, or dirty filter and algae.

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Skimmer is clean (so is pump basket and filter). I always have a skimmer basket, so a stone seems very unlikely.
I haven't had algae since the replastering 5 months ago, and the filter grids showed no algae when I cleaned them. Just fine dirt and debris that escaped the pump basket.

mas985 said:

The pump basket not filling during priming phase is usually caused by one of several things.

Suction side air leak
Impeller Clog
Return side blockage (filter or other)

Having a small single suction line can increase suction side head loss and decrease pressure in the pump basket making it more likely to leak air in. Check the pump lid gasket for cracks and lube well. A clog in the suction line can also cause the same issue.

A clogged impeller, dirty filter or other return side blockage does not have enough flow rate to purge the air in the pump basket. You may need to separate the wet end from the motor to determine if there is an impeller clog.

What is the filter pressure?

BTW, you should not need a priming valve for only a 1 foot lift from pool to pump.

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Thanks, mas 985.

*Of the 3 reasons you gave, I think the Impeller clog is a real possibility. This needs to be looked at. Can I cut off the power and stick my fingers in there from the basket side and determine if there is an impeller clog that way? Trying to not have to disassemble the pump.

Pump lid gasket was bought new last week and replaced the previous one, even though the previous one looked ok. Cleaned all gasket connections and relubed gasket/O-ring before installing. As far as I know there is nothing clogging the suction line -- water seems to flow pretty freely in both directions.

Filter pressure is 26 PSI at 3450 RPM (priming speed and "quick clean" speed). As I said before, I am surprised that the pressure never goes above about 27 PSI even with a very dirty basket and very dirty filter. The lack of pressure increase is the main reason that I went so long without cleaning either one. The gauge reads progressively lower pressures at lower RPMs, but maybe the gauge is defective??

Thanks for the reassurance about not needing a valve for that short lift. I know you are the resident expert on the physics of system head, etc.

I hope to hear your (or anyone's) input on the easiest way to test for the impeller clog. Shouldn't I be able to spin it easily by hand from the basket side? ...Or not?

Many sincere thanks to all for helping me with this priming issue.

OCLT results:

Last night:
FC 4.0
CC 0
TC 4.0

This morning:
FC 4.0
CC 0.5 (this may be erroneous, since I waited a few minutes before reading CC. Also, it has been 0.0 for months (and was last night also).
TC 4.5
CH 275
TA 100
pH 7.6
CYA 50 (dot was barely visible at 50 but not at 40, so I think we call it 50, is that correct?)

I will add a half gallon of 12.5% chlorine after I write this+. A warm sunny day is expected today.

If anything looks irregular with the balancing, please let me know.

Thanks for the Pump Basics link. Very informative.

Got it. Ok, will add a gallon.
Did I calculate CYA correctly?

I might have found something that contributes or causes the priming problem.

There is a check valve after the filter at the back of the crowded equipment pad (out of sight, out of mind). I noticed today that it stays closed during 1700 RPM runs and is only half way open during 3450 RPM runs. I think I will remove the cover and either remove it completely or inactivate one-half of the double-sided spring. Will let you all know what happens.

By the way, is it advantageous to have a check valve at this location (between the filter and the heater)?

Also, I noticed today, after running at 1700 RPM since yesterday, that the water level in the basket is much lower now. Looks like it is down to the top of the inlet pipe now.

PoolStored said:

Post some more pictures of your pad from different angles so we can see everything.

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Here are the pictures.
The first one starts at the front-left position facing the pad, and successive pictures rotate around the pad in a counter-clockwise direction.
I labeled a copy of the third picture to help you figure out the tangle.

@mas985 Yes, I do have a solar heater on the roof, but I haven't actually ever tried to use it since buying the house in late 2021 (basically just afraid I will open a whole new can of worms if I send water through that thing).

I'm kind of bummed out now that the check valve probably isn't the problem and I am back to a suction air leak. Would it not help the pump air problem (and not create a new problem if I ever use the solar heater) if I reduced the spring tension on that check valve?

Any other idea besides a leak under my concrete patio (26 feet from skimmer to copper pipe at the pad)??

mas985 said:

Pump Lid Gasket
Pump Drain Plug Gaskets
All suction side valve o-rings

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Thanks. I will look hard again at the lid gasket (it's brand new and lubed). Should I try tightening it farther than the handles being 90 degrees to the pump's length? It's tight at 90 degrees, but it could go a little farther by hand/arm force due to the lubing.

I have not examined the drain plug gaskets yet (beyond flooding them with water), so I will examine and lube them.

I will also try to determine if the impeller has debris in it.

Hopefully, one of those is the problem. I don't have a suction side valve.

mas985 said:

If you can hand tighten a little more, that might help. Just be cautious of using too much torque.

Is there a union or threaded pipe on the front of the pump? Those can leak as well.

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I'll tighten the lid a bit more without putting a crazy amount of force on it.

I examined that union at the front of the pump. The thick rubber gasket there looked fine. I re-lubed it and re-installed it. I tightened the union collar/nut as far as I could by hand.

There is a slight, but perceptible, difference between the main drain and the skimmer. The main drain setting has a bit more air, since I see little if any "rolling water" up onto the clear plastic portion of the lid during 3450 RPM speed. When I switch to the skimmer setting, the water rolls up onto about half of the plastic dome. I can then switch again to main and the water level drops back to not reaching the dome, and switch again to skimmer and it does reach the dome.

Note that the diverter is by no means a perfect diverter. It fits rather loosely in the pipe below the skimmer. Even when I set it to main drain, I can still see some water being drained from the skimmer (much less than when at the skimmer settiing, but definitely noticeable nevertheless).

But at neither setting does the giant air "bubble" disappear when I stop the pump. When stopping the pump under either setting, the water level is just below the dome (so the entire dome is showing air and no water contact). I think the pump is actually "primed" (ie, it is pumping only water and no air to the filter as far as I can tell), it is just that it's never able to remove most or all of the air in the basket area (as it should). Seems like there is a small suction air leak somewhere.

I will work on the drain plugs in a little bit and give an update on that, as well as the impeller.

EDIT: here is a diagram of the drain system, if it is not already clear. The plastic diverter slides into the pipe just below the skimmer.