No suction with vacuum

  • Last Post 22 January 2021
Kev70ss posted this 17 January 2021

Hello, for the past few years I have been chasing down this issue and can't figure out what it is. I have asked my pool guy to take a look and he has given suggestions but doesn't seem like he knows the equipment issues that well. This is an in ground pool with a pentair pump. Pool only with so spa or valves. What he suggested was to put a plug in the skimmer tee section of the pipe that runs down to the drain so it blocks that off. I gave that a try and no luck. I asked him about changing the pump and he said it's still fine.

The issue I am having is the pump will not prime with the vacuum attached. Works fine as a skimmer and the filter reads about 30psi. As soon as I plug in the vacuum it drops down to 5-6psi. So far what I have tried is replacing the vacuum and hoses, changed the basket seal on top and a few seals inside of it. Didn't quite do a full rebuild though. Changed the seals in the backwash valve, Changed the filter panels. The only way I can clean it is with the backwash valve open but suction is very low. After I suck up all the dirt in the bottom and switch it back to normal operation the outlet blows dirt back into the pool for a few minutes. I have to hold a vacuum hose onto the return outlet for a couple of minutes so the dirty water flows out of the pool and not back in. I think that's due to lack of pressure. 

Somewhere it is sucking in air and the last place I can think is the suction pipe running from the skimmer to the pump under the concrete. Anyone have any ideas where to look next?

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Kev70ss posted this 17 January 2021

Also forgot to mention when the pump shuts off water drains back into the pool 

InyoRob posted this 18 January 2021

We'd be glad to assist you. It sounds like there are a couple of potential issues with the pool. When the vacuum is attached to the skimmer, the pump doesn't seem to get enough water and that could be why the PSI would drop. Do you have a main drain? If so, can you open the flow to the main drain when you are vacuuming? That way the pump can pull more water.

The water draining from the system after the pump shuts off is a sign of a leak. A leak on the pressure side of the system should show up when the pump is running because it would leak water. The pressure side is everything after the pump.

A leak on the suction side would be at the pump lid or before the pump. 

Kev70ss posted this 18 January 2021

That was one of the things I looked at too. I do have a drain and I pulled the cover off and it was plastered shut for some reason. I thinking at one point it did work and the replastered the pool and covered it up which is weird. 

the o ring to my filter lid is a little worn so I am replacing that next to help seal up the pressure side. I read a few things online about wrapping the suction pipes with plastic wrap to see for is pressure changes and spraying each union/ opening with shaving cream to see leaks. I wasn't able to find anything 

InyoRob posted this 21 January 2021

Do you plug the vacuum hose directly into the skimmer port or do you use a vac plate on the skimmer basket? Using a vac plate on the skimmer basket may allow the pump to get a little more water.

Kev70ss posted this 22 January 2021

It plugs right into the skimmer port with a regulator. It's about a 3 inch pipe coming up from the concrete that it connects to.