Water level in inground pool rose at least 2" overnight. Any idea how?

Pete20745

Member
Jun 28, 2014
8
Holland michigan
Does your pool have an autofill?
No auto fill. We have gotten slammed with a lot of rain last weekend but no rain since. I'm thinking groundwater coming up through bottom drain? We had pool drained last year and had it painted. Painters had to set up a ladder across pool rigged to a pump because water kept coming up through bottom drain.

It was fine this morning. It did not rise at all. After doing yard work I noticed it filled again worse than yesterday! That happened within the last 1-2 hours. Thoughts?
 

JamesW

TFP Expert
Mar 2, 2011
19,362
Do you have a picture of everything?

What is the ground water level relative to the water level in the pool?
 

Pete20745

Member
Jun 28, 2014
8
Holland michigan
Do you have a picture of everything?

What is the ground water level relative to the water level in the pool?
I have no idea. The ground in back of my pool drops in comparison to the pool level. I am surrounded by woods/trees and for the first time water is actually pooling in my woods area.
 

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JamesW

TFP Expert
Mar 2, 2011
19,362
Definitely odd.

Unless you have an unknown fill line, it seems to be a mystery.

It doesn't seem like ground water would be getting in the pool because the ground water would need to be higher than the pool water.

Periodically, check the water meter to see if it's running when it shouldn't be.
 

PoolNewb2020

Well-known member
May 7, 2020
167
Lathrop, CA
Your pool may have a hydrostatic relief valve in the main drain. In places where water table is high, it prevents pressure buildup on pool shell and instead lets ground water inside the pool.
 
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JamesW

TFP Expert
Mar 2, 2011
19,362
Based on the terrain, ground water intrusion seems unlikely.

Maybe a picture of the system would be helpful.

Any chance that the pump is connected to a ground water well point?
 

Pete20745

Member
Jun 28, 2014
8
Holland michigan
Here is a couple pics of system. Thank you all for your responses and enjoy your Memorial Day!
Your pool may have a hydrostatic relief valve in the main drain. In places where water table is high, it prevents pressure buildup on pool shell and instead lets ground water inside the pool.
I b
Your pool may have a hydrostatic relief valve in the main drain. In places where water table is high, it prevents pressure buildup on pool shell and instead lets ground water inside the pool.
I bet you are %100 correct. We just researched thathydrostatic relief valve and your answer sounds dead on correct. Thanks!
 

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JamesW

TFP Expert
Mar 2, 2011
19,362
For ground water to come in through the hydrostat, the ground water would need to be higher than the pool water.

I don't see how that would be possible with the terrain.

Maybe if the main drain had enough suction, it could pop the hydrostat and begin sucking in ground water.

Is the main drain cover open or closed?

Are you putting a lot of suction on the main drain?

Maybe the pump is connected to a well point so that the ground water can be controlled during a drain. That's the only plausible way that ground water would get in the pool.

Are you 100% sure that there's no fill valve?

Do you know what every pipe at the equipment pad goes to?

Why is the pump plumbed with galvanized steel? That's going to add a lot of iron to the water.