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?