Need Help Figuring Out Where This Leak Can Be!

jaberkley · Postby **jaberkley** » Thu 17 Mar, 2011 16:28

Ok so I have a 20,000 gallon gunite in-ground pool. Only when the pump is running we lose water. The water level will drop down just below the skimmer level and then stop. We then have to turn the pump off for obvious reasons. I had a professional leak detection company come and do a pressure check on my lines. Both the suction and the return lines checked out perfectly, no leaks detected. The pool is extremely green because we have let it set since last summer knowing the problem would be rather expensive. We have only been in this home for 3 years. In the skimmer, the main drain plug has been plugged off by the previous owners. Which makes the leak detection specialist believe at some point there was a problem in the main drain. He is telling me my next step to try and figure this problem out is to have the pool drained and he needs to check the main drain at the bottom of the pool and see if that has been plugged off, and if not he will plug it off. My question is if this infact is the problem is it possible that we would only lose water when the pump was running? We are all completely stumped as to where the water is going, and why it is only losing water when the pump is running. I am willing to drain the pool and do what it's going to take but I am worried I will spend a lot of money doing this and it won't be the problem. Is there any other explanations as to where the leak could be? There are no structure leaks, and as I mentioned zero water leaves the pool until we turn the pump on. Any insight to this problem will be much appreciated!

jaberkley · Postby **jaberkley** » Thu 17 Mar, 2011 16:31

One more thing I forgot to mention, the leak detection specialist also said once the pool is drained he can check the light fixture, but doesn't see this as being the problem because the water level does not drop until the pump is on. We are trying to figure this out by the course of elimination.

Postby **Larry** » Fri 18 Mar, 2011 08:07

What kind of filter valve setup do you have?
You could be losing water through your waste line as a result of a leaky multiport valve.
If the problem is not on the waste line then you have a real no-brainer!

Larry

jaberkley · Postby **jaberkley** » Fri 18 Mar, 2011 18:53

We have a DE filtration system with the pentair multiport valve. My husband is going to cut the line to the backwash and run the pump to see if infact the water is just dumping over into that line. If this is the case then we will first try and replace the gasket, if that doesnt work then we will just replace the valve. I am hoping this will prove to be the case otherwise we will be completely stumped!

Postby **Larry** » Sat 19 Mar, 2011 06:37

Even new multiport valve gaskets can sometimes leak a little and often rather than replace the whole valve, we add a regular valve to the backwash line.
This is much easier and cheaper than a new multiport, and we have had no problems doing this up to now.

Larry

Postby **ChuckGeo** » Fri 08 Apr, 2011 07:57

If there is no leak through the multiport valve, the next thing to do would be a pressure test of the return (and pressure side cleaner) lines. Leaking only with the pump on is definitely symptomatic of a multiport leak to waste or a leak in the plumbing on the pressure side of the pump and filter - return line.
Also, you state that the water stops leaking "just below the skimmer level", which is when you turn off the pump. I just want to confirm that if you fill the pool to it's normal level and leave the pump off, that it does not leak over a 24 hour period. Next, measure the loss over 24 hours with the pump on. If the leak is in the return line, your measurement with the pump on will be significantly larger than the "off" measurement.
Let me know what you find.

Patm · Postby **Patm** » Mon 09 Jun, 2014 08:25

Thank you all for the posts regarding loss of water in your gunite pool. I've been chasing what I thought
was a leak forever. After reading your posts, I took apart my multi-port and sure enough the gasket
inside which separated the ports, was worn away. So, when the mupti-port was in the filter position,
the waste chamber was receiving water and we were losing water right there. And, a lot of water, inches
per hour. THANK YOU! The gasket was $10.