water leak got me stumped

[Sharonjh]

Hi all,

I've been trying to find a leak in my friends fibreglass pool. He was losing a lot of water. We plugged the skimmer and the water loss stopped so assumed it was a suction side leak. Have since pressure tested the suction side and there seems to be no drop in pressure. The pool also has a spill over spa. When I tried to pressure test the suction plumbing for the spa I couldn't even put pressure into the pipe meaning there must be a leak there as the water must be coming out as fast as its going in. If the spa plumbing is leaking why would he be losing water from the main pool? and when we plug the pool skimmer the leak stops.

Also this pool has a problem with pump priming. Every time you start the pump you have to prime the pump yourself with a bucket of water. I'm assuming the priming problem is a result of the leak some where.

Anyone got any ideas what to do next?

 

[needsajet]

Is the pump higher than the water line of both pool and spa? And can you see any leakage after shutdown from the drain plug on the pump?

And speaking of a lot of water, how much are we talking about? 5 or 6 mm per day, 35 mm per week, sort of thing? Or does it drain down below the skimmer throat overnight or within a day or something like that?

 

[Sharonjh]

Pump is higher than the water line. The pool guys that came out installed a non return valve in the suction line to see it that helped with priming but no luck.

In regards to the leak, it drained down past the skimmer throat overnight. I think the pump was on all night. I'm not sure if it leaks with pump off cos we plugged the skimmer in the morning when the water went down. Did notice a leak at the backwash hose when the pump is running. We will have to take the plug out and see if it loses water with the pump off.

 

[aussieta]

if the water is coming out the backwash hose when pump running then the multiport valve gasket has most likely failed

 

[needsajet]

Yep, that's helpful information. If the spider gasket in the multiport valve is leaking, you will lose water through the backwash hose when the pump is running. It's also possible, with the pump off, for water to siphon out if the backwash hose is lower than the water level of the pool (if the system is otherwise airtight). Once air can get in, the system will then drain down including the pump strainer basket.

 

[Sharonjh]

I would say that the backwash plumbing is lower than the pool level. I say "plumbing' because instead of having a hose it has pvc piping which goes underground into the street run off. Interesting set up. We are going to replace the spider gasket so will let you know how we go.

 

[needsajet]

My multiport valve (MPV) doesn't have the best reputation, so I added a valve on the backwash line. You have to remember to open it when backwashing, and then close it after, but it prevents any leakage or siphoning. My setup is similar with a backwash pipe below pool water level.

I had a problem with draining down a while back, but mine turned out to be a poor seal around the collar where the MPV clamps onto the filter body. It allowed air to get in, so the system could drain down between pump runs (no water drips though). I could hear gurgling after the pump shut off, which helped me find the problem.