Sand filter pressure going up really fast


In The Industry
Apr 7, 2021
South Texas
Hi ya'll Im new to this forum but I have gotten some useful information from it. I've got a problem with a customers equipment, when I first got there the pool was green, so I treated it accordingly but the pressure of the filter was going way high. After removing the valve I found out the sand was gross and it hasn't been changed in forever, changed the sand, checked laterals and valve, everything was in good condition, then after letting it run for a while the pressure jumped from 20 psi to 30 psi in less than an hour, I thought well the filter is a small one so its filtering all the debris and algae out, but then the psi was jumping to 30 psi in a matter of 15 minutes, I checked for leaks and obstructions and I couldn't find anything. Any ideas of what i can do to fix that issue? The pump is a pentair superflo 1.5 hp and the filter is a hayward s166t that's 100 lbs of sand. Some people have told me the filter is too small for that pump but the equipment was working fine before and after backwashing the pressure goes down and the return lines shoot water normally, but when the pressure hits the 30 psi you can see how the return lines don't shoot that much water.
Any help would be greatly appreciated and I'm just here scratching my head trying to figure it out.

Thank you very much in advance!


Gold Supporter
LifeTime Supporter
TFP Guide
Jul 3, 2013
Southern OK
Welcome to TFP :)

The filter is doing its job and as it filters the gunk and algae out the pressure will rise... Because it is small is the reason it is doing it fast... As the pool gets clean and algae free the pressure will rise slower :)

How is your SLAM going?

SLAM Process
Overnight Chlorine Loss Test