Need help with leak detection

[Deleted member 62417]

I have 25 year old (approx.) 18' x 36' in-ground pool that is losing water while the pump is running. I am losing about 1/8" - 1/4" over 12 hours. I have compared this to a bucket of water, the bucket does not evaporate appreciably so I know it is not evaporation. Also, it loses water when covered and it is a new phenomena (i.e. hasn't been a problem in previous summers). I plugged all the returns and the skimmer basket and turned the pump off for 24 hours with no loss. This indicates that there is no liner leak. I ran the system in with my valve on recirculate which had no effect, i.e same water loss over 12 hours. I see no water anywhere so I am a bit stumped.

One thing to mention is that when the pump timer turns the pump off from filtering the pump basket drains back into the pool quickly. This does not seem right since the air, and alot of it, must be coming from somewhere, but I can't determine it.

A second thing to mention is that I don't know whether my bottom drain is working or not, I don't know whether the previous owner blocked it for fear of children being stuck to the bottom. Apparently this was common around here.

A third thing, there is a circular plastic piece screwed into the bottom of my skimmer basket that has a hinged piece over the drain line and a hole over the return line. The gasket on this is really bad. I don't know what this piece is for (can anyone help with what this is), but it is definitely sketchy. Could that be a problem? See attached photos.

Equipment:
Hayward 1HP Superpump (just installed by myself)
1-1/2" lines
Hayward 220t sand filter (pretty old i imagine)
Watermaid Salt Water Chlorinator

HELP

Derek Jenkins
[email protected]

 

[Thimble]

Is your skimmer and main drain plumbed independent from each other....do you have a valve that opens/ closes each one ? If you do, you could close one and leave the other open, run your pump for a cycle and see if your level drops. If not, switch which valve is open/closed and repeat. This would give you a clue if the leak is in you skimmer or main drain.

You might check your spider gasket on your sand filter, too. Could be the source of your air leak and possibly water leak ( as in the water is going to waste while pumping due to a bad gasket letting it cross over when it should not).

 

[Deleted member 62417]

I don't know what the main drain is. I have the two lines in my skimmer as shown, one to the bottom drain and the other is the return to the pump. So I guess not since the only return to the pump is coming from the skimmer.

I thought about the spider gasket. I had one wear out a couple of years ago. I inspected it and it looked OK, but you cant' really tell by eye.

 

[Agent99]

The main drain (it isn't a drain...dunno why it is called that) is normally in the deepest part of the pool and it, well, looks kinda like a drain. In your case, the MD is plumbed to the one of the skimmer ports. The other skimmer port heads back to your equipment pad and into the main pump.

That doohicky in your skimmer helps to regulate the flow between the skimmer and the MD and it also likely protects the pump from running dry should your water level drop below the skimmer or the skimmer gets clogged or something basically happens that no water is flowing through your skimmer. The water will then come from the MD and your pump is happy.

Help pool losing water fast!!!! Check this post (posted nearly the same time as your post) where I make a couple of suggestions on how to isolate and/or pressure test plumbing.

Skimmers can leak right at the ports you see there. Look very carefully with a strong light to see if you can see anything. You might find a crack/split along the port.