I feel that I'm replacing more water than usual and will be starting with a bucket test this weekend. My question is regarding a pressure side leak and wondering if I can eliminate it based on this assumption and observation. I notice the loss of water is overnight, I filter during the day, can I assume a pressure side leak would have greater water loss when the pump is running?

We have been experiencing temperature swings from hot day to cool night and I've read that can also account for higher evaporation.

Either side leak, if in the plumbing, would usually be more prominent when the pump is running. Most leaks are around the skimmer and light though, if that helps you any. That is where both of mine were.

The skimmer was repaired when I first bought the house 10 years ago, hmmmm, you can see the patch from the skimmer to the pad. Depending on my results this weekend I'm starting to think it might be worth bringing in a leak detector. I'm preparing for a remodel but need to get this figured out first. Thanks!

So I've confirmed the leak and it does leak more overnight when the pump is off. I'm suspecting the skimmer like RobbieH mentioned. I'm guessing that when the pump is on, water running over the leak is slower to leak out as opposed to still water with the pump off. Any way, since I was looking to remodel, I'll have the plaster compnay deal with the leak too, I've confirmed they do leak detection too. Hopefully it's not too expensive and effect the amount of remodel work I will be able to get done.

*edit* Just got off the phone with the estimator and the plaster folks don't do leak detection. Tonight I'll plug the returns and if it's not them I'm going to shut off the pump for a few days and watch the drop in water level. If it goes much past the skimmer I will call out a leak detector.

I've had good results with food coloring. Turn the pump off and let the water get still, then squirt food coloring around suspect areas. It WILL go to the leak and you'll see it immediately.

Skimmers leak all the time. It's caused by the difference in expansion between the deck and the wall of the pool. The leak can be tested with dye. Can be fixed (temporarily) with epoxy at the junction between the skimmer throat and the outside of the pool.

If the pool is being replastered, a more permanent (but still temporary) fix is to force water stopping cement into the voids around the skimmer, then "white in" the skimmer inlet (to the skimmer throat) with plaster.

Thanks all, I did put die where the skimmer meets the pool and I could see a slow leak. I plan to epoxy for the short term and to be sure I have no other leaks.

Qwaxalot, is a skimmer replacement the long term solution? I am considering it as this effort made me take a closer look at my skimmer and I do see cracks on the back of the skimmer wall (area furthest from the pool) but they are above the water line. I think those were self inflicted as my vaccumm plate is slilghtly larger than the skimmer opening on the deck and I give it hard tap with my hand to get it in.

Can just the skimmer be replaced, or should the plumbing to the pad also be replaced?

Yes you can replace the skimmer, but it is NOT trivial, and may well not be a permanent solution.

The trick is to cut the deck around the skimmer, so that there is enough room to get the old skimmer out (you'll have to cut the plumbing to get it out); then you have to figure a way to solidly attach the new skimmer to the outside of the pool; then, when you patch the deck you have to make sure that there is enough expansion to ensure that the patch and the new skimmer won't be moved as the rest of the deck expands and contracts.

Whew, sometimes reapplying a little epoxy once a year is not so bad

Edit: No you usually don't have to replace the plumbing to the pad.