HIGH PSI on sand filter

  • Last Post 10 July 2021
Stafany posted this 29 June 2021

Hi All, 

First, please excuse my poor language. French woman in USA  need to learn a lot to improve her knowledge. 

And about knowledge, let's explain my problem : 

My pool system, built 5 years ago, has never been in trouble. A month ago, I noticed the filtration PSI (before at 13) moves to 25, without any modifications. I used to clean filter at 15 and backwash did nothing. To try to solve the problem, I bought new gauge, then new sand ,then new multiport valve. Nothing happens, same high pressure without any explanations. 

PSI are : filtration (25) backwash (12) rince (17). Recirculation position and closed position of the multiport valve have a very bad issue : the pressure is so high that multiport valve becomes stucked. 


Am I right  with the following : 

1. They are only 4 possible causes of high psi : filter, inlet pipe, inlet nozzles, multiport valve

2. If in the rince position (so without inlet system) there is still high psi, the inlet pipe and nozzles are not the cause

3. if sand has been changed and the grinds checked,  the filter is not the cause

4. And if I have already bought a new multiport valve .... I have no more cause to my problem. 


Can you help me to find a solution? 







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JCMC70 posted this 29 June 2021


 I can think of one additional possibility. If there has been a check valve installed in the pool plumbing and that valve is malfunctioning or broken, that could cause a spike in filter pressure.

There are other items you can check in This InyoPools article


Stafany posted this 01 July 2021


thanks for your answer 

I´ve tried your idea. I've got 3 check valves (vacuum, tank, and after the pump) and cleaned them) They seem good. 

Checked too the other items in the Inyopool article 

In this case it could be a small leak air succion. Where? For me can be only just before the pump because high pressure occurs in all positions (infinity pool, main drain, recirculate, rince) and on all pipe I've got valves. I checked with incens not easy because of the air from the pump, checked too with soapy water but cannot find anything 

I am there 

can't understand what happens 

Service posted this 06 July 2021


Here is a Video on How to Help Find Pool Suction Leaks which you may find helpful.

Thank You



Stafany posted this 10 July 2021

Thank you. I tried it on the succion lines. Couldn't find anything wrong but my pressure is still very high ! 
according to previous checks :

. succion lines : ok because Pressure is still high with main drain or tank or vacuum 

. return line : ok because pressure is still high when I rinse filter (means when I don't use return line) 

. filter : ok because pressure is still high which recirculation on the MPV

. MPV : ok because it's a new one and I've already checked it 

Is there anybody with a good idea to solve this problem ? 

Many thanks