Leaking pool

[cma20]

We just moved in to a new home with an inground pool. We had to do some work to get the pool ready for use and did it ourselves (cleaning, patching, plumbing). Everything looked great so we filled the pool. The morning after we filled the pool, we realized we lost more than 2 inches over night. I thought I had it figured out that we had a suction side leak as it seemed like we only lost water when the pump was off. I plugged the skimmer holes at night but this did not help. I decided to let the water leak as far as it would go until it stopped. It stopped about 5 inches below the skimmer boxes, several inches below the return outlets and about 2 inches above the light. This told me, or so I thought, that the pool itself was not leaking, but it had to be the plumbing.

Looking at the pool I realized that the water seemed to stop leaking at where I would figure the underground plumbing would be. But this doesn't make sense to me. If it were the skimmer lines, then it seems to me there would be no water in the skimmer boxes - but there was. If it was the pump side, then how did the water level drop several inches below the return lines? What else IN the pool could be leaking? Could it be the steps? It doesn't seem reasonable to me that it was the main drain because wouldn't the water leak all the way if it were?

Yesterday, I opened up the lines going to the pump and they were full of water - above the ground. So doesn't that rule out a leak in the skimmer line?

I know the easy thing to do is to call a Leak Detection Company, which is what I did, but they cannot come for a couple weeks, and they want a minimum of 400.00 for the first hour, then 115.00 for each additional hour. There has to be some logic to this.

Can someone please help me think this thing through?
Thank you!

25,000 gallon inground with vinyl liner
Pentair pump; sand filter

 

[zea3]

Check the liner carefully at the waterline and look for tears in the liner and leaks around the steps. You can use food coloring to see if it gets sucked into the steps where it meets the liner, and to check any seams in the liner. Since the leak stopped well below the skimmers and returns, I don't believe your plumbing is the problem. In a vinyl liner pool the leak will be at the waterline where the pool stops leaking. Be sure to inspect the steps and check all around their perimeter with food coloring.

 

[cma20]

Thank you for responding. I will check the steps today.

 

[cma20]

I put red dye all around the steps today and did not see any evidence of a leak. We are supposed to have some cool days this coming week - 52 degrees in July - I think I'll let it leak again until it stops then check it again. Would a pool leak faster with more water in it? Does a leak slow down as the amount of water in the pool decreases?

 

[zea3]

I wouldn't add more water just to watch it leak out. Let it leak until it stops, however don't let it leak past 1 foot deep in the shallow end. If the leak has appeared to slow way down it may have reached the point of the leak and the rest of the water loss may be evaporation. You can check if it is just evaporation by doing the bucket test. Partially fill a bucket with pool water and set it on the steps of the pool near water level. Mark the water level of the pool on the outside of the bucket, and mark the water level of the bucket on the inside of the bucket. Turn off the pump for 24 hours. Mark the current water levels of the pool and bucket. Compare the amount of water lost in the bucket vs in the pool. If the water loss inside the pool is greater there is a leak in the pool. (example, if you lost 1 1/2" inside the pool but only lost 1/4" in the bucket that would show a leak in the pool.)

 

[cma20]

Thank you. I'll try this.