Identify this circle thingie on pool bottom

Melnic

Silver Supporter
Jun 7, 2017
205
Maryland
#1
I have 2 of these near the main drains and one in the shallow end. What are these small circle thingies with the line through the middle?
 

MinerJason

Bronze Supporter
Jan 29, 2018
150
Tucson, AZ
#4
Looks like hydrostatic relief valves/plugs to me. If you have a high water table, draining your pool can result in the pool shell literally being pushed up out of the ground by the surrounding water pressure. In such cases, hydrostatic relief valves are put into the shell, which allow water pressure to equlaize in the event that the pool needs to be drained for repair, replastering, etc. Sometimes they're an automatic spring loaded check valve type device, and other times they're simply a hole through the shell with a plug that can be removed.
 

Melnic

Silver Supporter
Jun 7, 2017
205
Maryland
#7
thx,
Property slopes to the back yard. The street is higher than the house is. The pool area was built up level with the dirt from the dig out and then it goes down hill from the pool. They went through great pains to have the house drains piped into 4" PVC all the way back to beyond the pool. Hopefully they did what they had to make it stable during construction. Hopefully.
 

PoolguyinCT

In The Industry
Jul 21, 2014
2,671
Connecticut
#8
thx,
Property slopes to the back yard. The street is higher than the house is. The pool area was built up level with the dirt from the dig out and then it goes down hill from the pool. They went through great pains to have the house drains piped into 4" PVC all the way back to beyond the pool. Hopefully they did what they had to make it stable during construction. Hopefully.
Building pool high is another tool for water jobs..