Pump Problem After Backwash

[PoolFrog]

Hi,

I backwashed our DE filter today, which is something that I've done many times before. Our system has a separation tank to collect the used DE when we backwash. I have attached a picture that shows our filter as well as the tank next to it. When I get ready to backwash, I turn the pump off, grab the black T-shaped handle on the pipe coming out of the filter, twist it 90° and pull upward to open flow between the filter and the tank. I turn the pump on, run it for about a minute, then shut it off. I push the T-shaped handle all the way down and twist back 90° to where it was. This was what I did today, as usual. Normally, when I turn the pump on again, things run just fine. Today, when I turned the pump back on, I noticed that the water in the pump strainer was very low (was water tight before the backwash), the pump was not as loud as usual, and the pump strainer wasn't filling with water as usual. I continued to run the pump for a few minutes, and never saw a change in the water level in the pump strainer area.
The filter also shows 0 psi now. Any ideas on what could be causing this?

I first attempted to do the backwash yesterday, but had a problem with the tank lid coming off. We determined that the rubber gasket was worn and needed to be replaced. I got a new gasket yesterday, put the lid back on and clamped it tight. It was getting too late to backwash yesterday, so I made sure that the flow from the filter to the tank was closed so that the pool could run normally last night (which it did). I let some air bleed out of the tank before doing the backwash today. Could this have had any effect on the pump problem that I have now?

 

[ajw22]

With your slide valve in the filter position the separation tank should be out of the loop and not effecting anything.

I would disassemble your slide valve and check and lubricate the O rings. Consider replacing the O rings.

 

[Bama Rambler]

The slide valve shouldn't have anything to do with the level in the pump strainer basket. as it's on the discharge side of the pump.
Is the water level in the pool high enough?
Is there plenty of water in the skimmer?
Is the skimmer weir door working properly?

 

[PoolFrog]

We've never had to do that, so we don't know how to disassemble that valve.

 

[PoolFrog]

Yes, the water level in the pool is normal. The skimmers are relatively clean (I've seen worse in the past during this time of year). The skimmer closest to the pump isn't having a problem with the weir. I can check the other skimmer later to make sure that's not an issue.

Someone that I was talking to wondered if it could be an impeller problem.

 

[Bama Rambler]

It sounds like a clog in the suction line or a suction side leak.
Did you pull the lid off the pump basket when you backwashed?

 

[PoolFrog]

Yes, the lid was opened and the pump basket was removed after backwashing when I first noticed a problem after starting the pump up again for normal pool circulation. I thought maybe the basket was full, so I emptied it to see if that made a difference.

 

[Bama Rambler]

Did you lube the o-ring when you put it back on?
Also make sure the o-ring is seated in the groove correctly.

 

[PoolFrog]

I will check that. I appreciate the suggestions. It's just so strange that the pump was primed before the backwash, but not since.

 

[PoolFrog]

We checked things out, and determined that there was a ton of air in the line. Something weird about that backwash that I did. The screw on top of the separation tank lid was a bit loose, and somehow this seemed to introduce air into the rest of the system even though the valve going from the filter to the tank is in the closed position. We ended up putting the garden hose into the skimmer that is closest to the pump and running water through while the pump ran. Eventually, we started seeing huge air bubbles coming out of the returns, the pump basket area started filling with water all the way to the top of the lid and we had filter pressure again.

 

[PoolFrog]

I would like to update this thread, as a similar thing happened again today when I was just emptying the pump basket. As I twisted the lid loose, I heard a gurgling sound coming from the separation tank. I haven't backwashed - the slide valve was untouched, so that tank should be closed off. When I removed the pump basket to empty it, the water level inside dropped way down. I put the clean basket back and closed the lid tightly. When I turned the pump back on, I couldn't get it to prime again. I had to do the same method of running water from a garden hose that was fed into the skimmer closest to the pump to get it to eventually prime after 5 minutes or so. I never used to have a problem getting the pump to prime after simply emptying the pump basket. Any ideas of what is causing this?

 

[Bama Rambler]

It sounds like the slide valve may be leaking internally. Did you ever open up the slide valve and check/lube it well?

 

[PoolFrog]

No, because we don't know how to do it. I have been wondering if that could be the culprit. What needs to be done to remove it?

I may need to do another backwash soon. Is it safe to do it if that valve is having a problem? I'm afraid of getting into a situation in which I can't close off the tank in order to be able to run the pool in filtration mode.

I'm also wondering if it could be as simple as the pump basket lid not being as tight as it should be. I twisted until it wouldn't budge, but maybe it's still not making a good seal.