Pool leaks when closed but is fine when it's working

[slvov]

I have a strange problem that puzzled me and my pool pro. When we opened our in-ground pool in the spring (we bought the house with the pool after it was closed) it was only about 1/3 full. We brought couple of trucks of water expecting that we will have to call a diver to find a leak, but the pool stayed full whole summer. I only had to add a couple of inches of water when it was very hot and dry in August.
Early September we closed a pool. A few days ago (little over a month after closing) I checked the water level and discovered that the pool is about half full (way below lights), and by the wet line on the wall you can see that the water continues to slowly leave the pool.
How is possible that pool leaks only when closed, but not when it's open? Any ideas are much appreciated.
simon...

 

[Jimrahbe]

S,

Do you run your pool pump 24/7 when the pool is open?

Thanks,

Jim R.

 

[slvov]

S,

Do you run your pool pump 24/7 when the pool is open?

Thanks,

Jim R.

No, I run pump about 12 hours a day (4 on - 4 off)

 

[ajw22]

Does your pool have an autofill?

 

[slvov]

Does your pool have an autofill?

Nope, I fill it with the garden hose.

 

[ajw22]

What things are at the 1/3 fill point where the water was when you opened it?

Water leaks until it drops to the point of the leak. The penetrations around that water level are where you need to look for the leak.

 

[slvov]

What things are at the 1/3 fill point where the water was when you opened it?

Water leaks until it drops to the point of the leak. The penetrations around that water level are where you need to look for the leak.

I would agree with that if the water continued to leak through the summer...

 

[Jimrahbe]

S,

My 'guess' is that you have a leak in your suction line... When the pump is running (12 hours) no water is leaking out, but when the pump is off the water leaks out. You assume it is just evaporation. When you close, your leak rate doubles, and you notice the leak more.

It could certainly be something else, but I can't think of any other leak that would cause the problem you are having.

Thanks,

Jim R.

 

[ajw22]

I would agree with that if the water continued to leak through the summer...

I would not get hung up on the question of why it leaks when closed versus open. That is a distraction and you will figure that out when you find the leak.

The fact seems the pool leaks when closed. Look at where the water stabilizes. 1/3 full is way under and suction lines. And if you had a main floor drain that was leaking the pool would empty more than 2/3.

 

[slvov]

S,

My 'guess' is that you have a leak in your suction line... When the pump is running (12 hours) no water is leaking out, but when the pump is off the water leaks out. You assume it is just evaporation. When you close, your leak rate doubles, and you notice the leak more.

It could certainly be something else, but I can't think of any other leak that would cause the problem you are having.

Thanks,

Jim R.

Jim, It sounds plausible, but i believe the water was blown out of suction line when the pool was closed.

 

[slvov]

I would not get hung up on the question of why it leaks when closed versus open. That is a distraction and you will figure that out when you find the leak.

The fact seems the pool leaks when closed. Look at where the water stabilizes. 1/3 full is way under and suction lines. And if you had a main floor drain that was leaking the pool would empty more than 2/3.

Is it possible that water line stabilizes when the hydro-static water pressure evens out? Could it be an issue with a hydro-static valve? Still doesn't explain why it doesn't leak in the summer.

 

[ajw22]

Is it possible that water line stabilizes when the hydro-static water pressure evens out? Could it be an issue with a hydro-static valve? Still doesn't explain why it doesn't leak in the summer.

Could be. If you have high surface water the water level would drop to the surface level.

 

[Lake Placid]

Jim, It sounds plausible, but i believe the water was blown out of suction line when the pool was closed.

A cracked main drain suction line wouldn’t air lock, allowing water to re-enter the pipe.

1/3 full is way under and suction lines. And if you had a main floor drain that was leaking the pool would empty more than 2/3.

If the main drain has a run upwards to the the pad the entire vertical depth of the pool, that line certainly could leak down to any level in the pool where there’s a crack in the pipe. In other words, if the main drain suction line is broken relative to the 1/3 level in the shell of the pool, the water will equalize in the pool and in the pipe at that broken/cracked level.

I tend to agree with Jim it’s the main drain suction line…

 

[slvov]

Crack in the main (bottom) suction pipe makes sence. But again, how would it explain that water doesn't leak through summer. Pump creating negative pressure may be slowing leak down, but the pump works only half the time, and for the period from mid July to the end of August when we practically had no rain, I only had to add about 2" of water. Compare it to losing over 2-3 feet of water over little more than one month.

 

[Lake Placid]

The pipe is under suction whenever the pump is running. Water won’t move out of the crack when the pump is running. A suction line leak makes sense for your symptoms. The shell would leak 24/7 regardless of what the equipment is doing. A pressure side leak would be more noticeable when the pump is on, not off.

Is it possible the leak was so slight that under suction you wouldn’t lose water and with the pump off it was barely a dribbler…then the crack was broken open worse when then pipes were blown out?

Pressure testing the lines will definitively tell you if they are leaking or not. Dye testing will diagnose the shell/fittings. As Allen stated previously, the why it leaks when everything is off is secondary to finding the leak and repairing it.