Pool Filter... filter. "Incomplete" prime?

July 15, 2009 12:57 PM

Replaced Jandy CJ200 cartridge filter with new Jandy SFTM22 sand filter. Pump pot no longer fills completely with water. Possible reasons? Contractor malfeasance?

This weekend my Jandy CJ200 shot its top half many tens of feet into the air for unknown reasons. We had just cleaned the cartridge like many times before and had restarted it. The pressure release valve was definitely open.

Whatever the reason for this event, we simply decided to buy and have installed a new 22" sand filter, the Jandy SFTM22, which is apparently a renamed Hayward due to some recent corporate acquisitions.

Our pool service installed the new filter and left, but the pump never primed, and we couldn't get it to do so using the normal methods. Note that we have a Jandy JHPU1.0 1 HP pump.

So we got the pool service out again today and they managed to improve the situation somewhat, so that the water level is higher in the pot, and completely covering the inlet pipe. They say they did this by sealing some leaks, but that to fix it completely they need to replace the diffuser. We did backwash the filter, but it is brand new and the water was perfectly clear. There is no pressure release valve on this filter, not that I know if it needs one. It is currently operating at 23 PSI, and has been since it was installed. No idea if that is normal since it is brand new.

Note that the pot filled just fine when the CJ200 was in operation.

So I have a few questions:
1) Can the pump/filter just be operated this way as long as the water completely covers the inlet pipe?
2) Could this be considered a normal consequence of switching to a new filter? Maybe the new filter is easier to pass water through?
3) Could excess pressure in the system damage the diffuser without noticeably damaging anything else except for the old filter?
4) Could this have been caused by the contractor during installation?

Thanks for any help!

posted by rocketpup to home & garden (3 comments total)

Sorry, I should also note that air gets purged out of the pot to a point and then it stops. Just above the level of the o-ring in the pot lid. Water occasionally glugs over bottom level of the clear plastic. The level of air does not increase or decrease once it finds its "sweet" spot. I can see no air bubbles coming into the water in the basket from anywhere. I also see no obvious water leaks anywhere that is evident around either the pump or filter.
posted by rocketpup at 1:01 PM on July 15

Really not something that I can fully diagnose without seeing, but here are a couple of possibilities and things to look for to trouble shoot.

One of two things is going on, either the pump (suction side (pot)) is drawing air in, and unable to fully pull prime. This means you have a suction side lead, o-rings, loose clamps, cracked fittings underground, or a clogged line.

(Typically a clogged line will mean a bit of surging so thats probably not it.)

The other explanation is on the pressure side of the pump, everything after the impeller of the pump - which includes the new filter. I suspect some restriction in the pressure side which is impeding the ability of the pump to push water through.

You can isolate the new filter as the problem, by stopping the pump, put the dial valve on recirculate/whirlpool and start back up - Does this allow the pump pot to fill up? (You are bypassing the filter media this way) - if it fills up - problem is in the installation of the new filter. (could be plumbed wrong, etc).

If recirculate is same symptoms, try same thing on drain. You will waste water during this test,you will waste water to see if the pump draws full prime, then there might be a restriction beyond the filter... is something like a missed valve restricting water flow back into the pool? Even could be filter IN / OUT connections reversed. (seen it)

If these don't work, could be a debris in the impeller (would assume pool company checked this, but who knows...my guys would probably have forgotten the obvious). Turn pump off, pull lint pot basket, feel with fingers for debris in impeller.

My gut is that you have a blockage/restriction past the filter, which raised the back pressure in the original filter to pop it... sand filters work different, and maybe the pump just isn't able to generate enough "push" past the restriction, (and doesn't draw full prime)

In answer to your questions.
1. Yes, as long as some water is circulating, which cools the pump you won't damage it.
2. No, not a consequence - there is a repair issue.
3. Plastic degrades over time, and the diffuser could be damaged, but so could the impeller, etc. Yes, a diffuser could be the issue - wouldn't be the first, second, third thing that I would look for though.
4. Yes, probably is an installation issue - certainly something that should have been dealt with during replacement, and trouble shot.
posted by dripped at 6:49 AM on July 16

Thanks, dripped. That's a great answer.

Then guys did check for and apparently repair a leak on the suction side which helped get it to the point it is at.

They did remove the motor assembly and check it out, which led to their diagnosis of the diffuser. You'd think they would have seen debris in the impeller but I will check.

I tried running it on recirculate for about 10 minutes with no discernible effect. Haven't tried backwash yet, but the pool guys did do a couple minutes with us when they came out and there was no noticeable effect on the pump either.

Thanks again!
posted by rocketpup at 1:52 PM on July 16