Need leak help

We have an in-ground gunite pool, approx. 20 x 40, that is about 20-25 years old. We bought the house last year so this is our second season with the pool. Last year there were no problems. This year when everything was started up the pool leaks. Once filled, the water level will drop to about 2-3 inches below the bottom of the skimmer. When filled, water will flow out of the waste (?) drain pipe that empties in the driveway at a loss of about 1-2 inches overnight. The water appears to be flowing faster now, but that could be due to all the rain we have had in the Northeast if the water gets into the drain pipe (pipe broken and/or perforated to drain groundwater). Water has also been coming up through the ground in the backyard.

I have had the pool service guy try to diagnose the problem and he has plugged up various returns, etc., and the water level still drops. I assume that the leak/crack would have to be at or above where the water level stops dropping. Could this be a leak in the underwater light, the top of which would be in the general area of where the water stops dropping? I would think that if the problem was simply a crack somewhere in the gunite the water would not necessarily be running out of the drain pipe in to the driveway (unless of course it is a perforated pipe to also drain groundwater).

I am at a los at this point. The pool guy is supposed to come back and go diving at some point. Meanwhile he has it rigged with a device that continually fills the pool when the water drops to a certain level; so of course, my water bills are astronomical. Any thoughts, advice, help, etc., would be greatly appreciated.

CH, welcome to the forum, after you've been around a while you should be able to save the expense of the pool guy and do everthing yourself!
From what you describe, the first thing to do is take apart the multiport, this is something you can easily do. First, get some silicone or teflon based lube (NEVER USE VASOLINE OR PETROLIUM BASED LUBE ON THE RUBBER O-RINGS OR GASKETS!!) Turn off the pump, close any valves you have so you don't flood or loose prime. Make note of the valve's orientation (there should be an alignment notch next to one of the screws) so you can put it back together correctly. Using a #3 phillips head screwdriver (#2 will also work), remove the screws (use your free hand to catch the nuts on the bottom) and keep the screws and nuts safe, perhaps bring a cup to put them in. Lift off the top of the multiport and look at the gasket (it'll have 5 -6 spokes) I'm willing to bet that at least one of the spokes is bubbled up or torn - this is why the water is pouring out of the backwash line. Inspect the channels that it sits in for warping or breakage, if there is breakage, you'll need a new multiport - if the spider gasket/ aka wagon wheel is damaged you'll need a new one.
If, on the off chance, everything looks fine, lube it (be generous) and put the top back on in it's correct position. Put the screws and nuts on all the way around loosely (the nuts should have locking ridges on one side - that side goes agaist the housing to lock them). Tighten one screw then the one directly opposite it, if 8 or more do north, south, east, west then the rest in pairs, if 6 just be sure to do them in pairs of opposites.
Getting the multiport fixed should lessen, if not stop the leak - mark the water level with tape and then check it the next day for loss - it's raining in Ct, if you get rain it ruins the test, unless you partially fill a bucket with water and mark it's water line. You can then compare the bucket level with the pool level, setting the bucket on the steps will keep the water temps ~ the same and give you more precise results.
This should get you started, if you need more help or have any ?s, I'll keep my eye on this thread and I'm sure others will be along to offer more help. We'll get this fixed!:) - Waste

You may also want to determine if it only leaks when the pump is running. From your description of the problem I also believe the multiport is leaking.

Looking at the multiport sounds logical, I will try that. I have noticed that it is extremely difficult to move the handle and have noticed some drippnig coming from underneath. Assuming a new multiport is required is that something I can easily get at the local pool supply store and install myself or once diagnosed is that best left to the pool guy?

Thanks for the help!

CH, the fact that the multiport handle is difficult to move only confirms my guess that the gasket is bad. The only thing that might hinder you from changing out the 'port is the plumbing connections. If you want to give it a stab yourself (and if it's neccesary), I'll walk you through it ( I do this stuff all the time as part of my job :( ;) ) It would be nice to know the multiport and filter manufacturer and type. Again, if you need any help with this project, just ask and I'll get back to you, or someone else here will happily give you the help you need. - Waste

Waste, thanks again for your help. I can't wait to get home and open her up to see. Two final questions: (1) did I misunderstand that it may only be the gasket that needs replacement and not the entire multiport; and (2) would this account for the water coming up in the backyard?

Thanks again!

CH, yes, it could be only the gasket (which would save you $). As for the water in the backyard, I don't know the plumbing so can't say for sure. That's why I suggested the bucket test to see if the pool is still losing water. Unfortunately leaks sometimes appear in sets, you fix one thing but the pool is still leaking - it's frustrating but you've got to tackle or eliminate one thing at a time, but I can almost guarantee you that the gasket in your multiport is shot. Sometimes leak detection can take weeks to find :( , but 'slow and steady wins the race'. I'll keep my eye on this and help as I can!

Well I opened up the multiport and everything appears fine. I attached a few pictures. I didn't lube it though as I have to pick some up. Any further thoughts would be greatly appreciated.

CH, thanks for the pics - they make it easier to see what you're dealing with. The channels all look good in the pic. The gasket itself appears solid, but in pic #2 it looks like some warpage on the right side of the large section (this is the part that protects the waste line when in normal filter position) - did you look at the sealing plate (the part that is in contact with the gasket) for irregularities? Something caused that warp on the gasket and it's in the right spot to cause the problem we've discussed. I've got a possible fix in mind, but want to hear back from you before I suggest it.
Slow and steady... we'll get to the bottom of this before your water empties to the bottom of the pool :D - Waste

Waste, thanks for all your help. The leak was actually found today. Apparently there is a 2" or so diameter hole in the side of the pool just below the water line that is believed to once be possibly some kind of cleaning equipment. In any event, the pool guy missed it on his first round of plugging up holes and when he plugged it today the water stopped running. At least now my water bills will be back to normal!

Thanks again for all your help.

CH, glad to hear it - sorry if I took you the wrong direction :(