1960s Concrete Pool Leak

[doctorlambo]

Ok....I have a concrete pool built in the 1960s. It is a "Lazy L" shape. It has a main drain, two skimmers, and two return jets. The skimmers and jets are on the same side of the pool. When we bought our house, the pool was abandon. It had not been used in years and it had a brick patio around it, which was also gone. We got it running and poured a concrete patio around the pool. It has worked great for years.

In the past year, I noticed a little water loss and thought it was from a lack of moisture and high temps. However, we just opened our pool and it is now loosing 1 inch per day. I am 100% certain it is not evaporation and there are NO leaks on any pieces of equipment. I have also isolated the main drain and each skimmer and the water loss still occurs and light bubbles come from the return jets. Therefore, I have concluded that it is coming from the return jet line.

Here is the issue. In the past year, I have some chipping in the pool coping, where it meets the concrete deck. The concrete decking has sunk about 1/2" in the past year. I thought it was from the sand getting washed out over the years, causing the the concrete to sink. However, I noticed today that the water on the waterline tiles is 1/2" higher where I thought the decking sank. In other words, I think my pool has slowly shifted over the past 20 years....not the decking.

So, I am certain that the shifting on this area has caused a small crack. Problem is, I dont know how they ran plumbing in these old concrete pools. In the center of the pool, there is a round fitting about 1 foot below the top of the pool. Its probably seized on with the years of paint. I know there is a Tee here that exists the pool to the equipment, but I dont know what it is for. Can anyone tell me if this is for the skimmers or the jets? I think this may be where the leak is at, but I need to figure this out before I drain the pool and try to open it.....or better yet....remove the decking and dig.

Any help appreciated.

[Teapot1]

From your description I doubt it would be skimmer side, how many skimmer pipes apear at the pad?
T's are more common on the return lines.

[doctorlambo]

I was able to get that port open. It’s where the skimmers meet in the wall and exit as one to the pump. Now I need to pressure test it

[Teapot1]

Ahh, someone took a short cut on the skimmers. Any leak may be a good time to add a single pipe for each skimmer. If you are doing any upgrade work I would also add more returns, 2 per skimmer minimum. You just wont drive that amount of water through only two returns which means your system pressure (friction) will be costing you in electrical bucks $$$. Also wearing out your pump sooner and not providing the best filtration. If you are stuck with just the two returns, open them up as large as possible and fit a pump speed controller if you can, you only need full speed for backwashing and 99% of the time you are in filtration