Curious water loss and gain within a week.

[m a hanson]

I noticed a strange thing last week, after all the rain ceased here in the Northeast, my pool water level was really good. Several days later, I was out there hooikng up the robot and noticed I had a 1" loss of water. Then a few days later, it was back to normal. I believe it happened a few months ago too,soon after I opened the pool, I noticed a water loss of about 4", so I started filling it on and off for 2 days ( I'm on a well , so I had to break up the fill times) and I went to start filling the 3rd day, and the level was above were I left it the day before. I know there was no rain for several days on both occaisions to "fill" the level back up. Anyone know what I am experiencing? Is my pool expanding and contracting due to the water table? This is the only explanation I can think of.

Inground 1975 vinyl pool, about 13000 gallons. Liner replaced 2017.

 

[Texas Splash]

Is my pool expanding and contracting due to the water table?

Perhaps. You have a main drain? There may be an issue with your hydrostatic valve sticking on some occasions.

 

[m a hanson]

Perhaps. You have a main drain? There may be an issue with your hydrostatic valve sticking on some occasions.

How do I determine that? And would that explain a 4" loss, and 2" gain back when I started and stopped filling the pool the first time I noticed? ( Assuming the fill I did added 2" and the remaining 2" came from ???) I'm not a math whiz but a 2" of water missing and reappearing in a 16x32' pool seems like several hundred gallons to me. Not arguing your point, just trying to understand.

 

[Texas Splash]

The purpose of a HSV is to allow pressure from below (high water table) to reliever pressure. That valve moves slightly and can at times show signs of wear or get dirty around its seal. Its worth checking if you've exhausted all other measures. Best to confirm now while you still have time before closing in a month or so. Dive down there, remove the drain cover, and inject some food dye around the area to see if it gets pulled out.

 

[Texas Splash]

 

[m a hanson]

 

[m a hanson]

Thank you for the explanation.