I have had a slow leak for over a year now. Have done the bucket test to verify that the pool is losing water faster than evaporation, and to verify that the loss occurs without equipment on.
The plaster is old and has several significant cracks, so that is a possibility. I have tried the food coloring test with the cracks but so far that has been inconclusive; I can't really see any food coloring entering the cracks. To me, that doesn't rule them out as a source of leak though...could easily be user error.
So as I was brushing today I noticed that the pool light doesn't fit tight against the niche. Sure enough, I can reach down and wiggle the light and it opens a crack a good .125" wide. So I followed a line straight from the light to the edge of deck and checked the soil to find that it is definitely moist, whereas the soil everywhere else around the pool deck is bone dry. Does it make sense to suspect the light niche? If so, where might it be leaking, and how would I go about diagnosing/fixing it? (BTW, I tried the food coloring test around the light housing as well with no luck. I'm either no good at executing this test, or it is unreliable. I will accept either judgement.)
Right now I'm attempting to remove the light, but the one screw I can see is being very stubborn.
EDIT: So I removed the light but as I suspected, it didn't help because I don't know what I'm looking for!