CH, CYA, Salt all decreasing

[AlexPowell]

Hi,
CH, CYA and salt are all decreasing in my pool. CH of fill water is 100ppm

Today:
CH: 200
CYA: 60
Salt: 3600

8 days ago:
CH: 250
CYA: 70
Salt: 4000

Is this conclusive evidence of a small leak? The salt test seems like a lot but I didn't fill it up that much in 8 days and the test is +- 200ppm.
Water level drops about 10cm every 3 days and I'd chalked it up to evaporation as it was the middle of summer.

 

[Mdragger88]

Time for the bucket test

Leak Detection

A number of things can cause leaks in your pool. You can learn tricks for leak detection and how to pinpoint where your pool is losing water.

www.troublefreepool.com

 

[AlexPowell]

Time for the bucket test

Leak Detection

A number of things can cause leaks in your pool. You can learn tricks for leak detection and how to pinpoint where your pool is losing water.

www.troublefreepool.com

Jug is in at exactly water level... Wish me luck

 

[Mdragger88]

 

[generessler]

Jug is in at exactly water level... Wish me luck

One thing is that if it rains with this setup, the test isn't completely valid because the sides of the container flare out. They'll act like a funnel. You really want a container with vertical sides. I've used a cut-down bleach bottle.

 

[AlexPowell]

No rain planned

 

[JoyfulNoise]

the test is +- 200ppm.

Double the test volume of the salt test (50mL instead of 25mL) and your precision is +/-100ppm per drop of reagent.

 

[an1vrsy]

Double the test volume of the salt test (50mL instead of 25mL) and your precision is +/-100ppm per drop of reagent.

I don't have my test kit in front of me but isn't the sample size 10 mL? Doubling the sample size would be 20 mL to get each drop +/-100 ppm?

 

[AlexPowell]

It is too close to really know - there is perhaps 3mm difference. I will leave it another 24 hours. The biggest decrease seems to be at night for some reason - this is when the pump doesn't run.

 

[Newdude]

The biggest decrease seems to be at night for some reason

Warm water and cool air makes for more evaporation. A breeze makes it even worse because the surface area increase from ------------ to ^^^^^^^^^^^^.

The bucket/measuring cup might be a little off due to the sides of the container stopping some breeze.

 

[JoyfulNoise]

I don't have my test kit in front of me but isn't the sample size 10 mL? Doubling the sample size would be 20 mL to get each drop +/-100 ppm?

Quite right. I always forget which test volume is which. Just double the volume and you cut the drop precision in half.

 

[AlexPowell]

What's the verdict? The pool water is lower for sure. What's interesting is the level went down more overnight than through the day. I'll leave it in there today also with the pump running.

In case it is a leak, I will not refill it with water until the water stops dropping - this should show me where the leak is. Before I filled it, the pool was a natural pond so I don't believe the leak is at the bottom of the pool. I am hoping that if it exists that it is in the skimmer box or associated pipes. I will also block off the skimmer box to main drain pipe as this is not used.

 

[mgtfp]

The biggest decrease seems to be at night for some reason - this is when the pump doesn't run.

If I'm interpreting this correctly, then this could indicate a suction side leak. While the pump is running, you might pull air in (or whatever is around the leak). Without the pump running, more water can escape through the leak.

Do you see lots of turbulence in the pump basket when the pump is running? More bubbles than usual for your SWG to come out of the returns?

And 10cm water loss in 3 days does sound a lot. Plus CH, CYA and salt going down, all seems to be adding up towards a leak.

 

[AlexPowell]

If I'm interpreting this correctly, then this could indicate a suction side leak. While the pump is running, you might pull air in (or whatever is around the leak). Without the pump running, more water can escape through the leak.

Do you see lots of turbulence in the pump basket when the pump is running? More bubbles than usual for your SWG to come out of the returns?

And 10cm water loss in 3 days does sound a lot. Plus CH, CYA and salt going down, all seems to be adding up towards a leak.

Congratulations! Water level went down to the bottom of the skimmer box, then the skimmer box emptied down the suction side pipe. The pipe to main drain remained full of water.
I noticed some water wicking up through the ground around the skimmer box in the sand around the pool tiling so I suspect it might be near the skimmer box but realistically it could be anywhere from the water level pictured to the lowest point. I believe the pipes go around the outside of the pool.

What is the best way to get this fixed up?

 

[mgtfp]

And the water level in the pool has stopped falling now?

Has the pump been running when the suction side pipe drained? I.e., was the pipe drained by the pump, or via a leak in the pipes?

When you fill that empty pipe with the pump off with a garden hose straight into the whole, will the water then disappear quickly, or will the water stay!

I think first we need to be sure that there is a leak. And then probably start digging. Not sure if there are other options.

 

[AlexPowell]

And the water level in the pool has stopped falling now?

Has the pump been running when the suction side pipe drained? I.e., was the pipe drained by the pump, or via a leak in the pipes?

When you fill that empty pipe with the pump off with a garden hose straight into the whole, will the water then disappear quickly, or will the water stay!

I think first we need to be sure that there is a leak. And then probably start digging. Not sure if there are other options.

Yeah the pump was not running once the water line got too low. I didn't do the garden hose test but can do that next time - I just let the water level rise again so I can run the pump once more and let the chlorine levels increase.

I did begin the journey of exposing the pipe though. Thankfully - it's all above ground and there will be no digging. Another good observation is that the skimmer box is 100% the lowest point of the suction line.

Going to attempt to gently expose the leak and see if it is very obvious and easy to fix.