Filter Pressure Rises after a few hours

[cwms27]

I just installed a Hayward sand filter in place of my old cartridge filter. It has been running for a few weeks but I noticed the other day that after about 3 hours of running the pressure would jump up to 30-35psi from the normal run time of 15. I figured it was time for a backwash as it has been about a month since install. I backwashed it for about 1.5-2mins, then returned the pump to normal operation the next day I noticed the same thing. so I did the same, backwash and return on. This seemed to fix the pressure issue. until about 3 hours later I noticed it high again. I shut the system down, let it sit for about 15 mins before I got back to it and when I restarted it without backwashing or doing anything pressure was fine and again ran for about 3 hours when I checked the pressure was high again. Does anyone know what might be causing this? Thanks in advance for your assistance.

[Pool Clown]

We need to determine whether or not this is a filter issue, or something down stream of the filter.   Your backwash valve should have a setting on it marked "by-pass" or "recirculate".  This position should take the filter out of the plumbing circuit.  Since the by-pass mode may also take the pressure gauge out of the circuit, we will need to determine a base line.  This is going to be very UN-scientific.  When the filter pressure is at its highest, reach down to a return and feel how forcefull the incoming water is.  This will be your baseline.  Now, turn the pump off and put it into the recirculate position and turn the pump back on.  Now begin to monitor the incoming water for the next hour, or how ever long it has been taking to develop the high pressure.  

Are you experiencing reduced flow out of the return over time?  If so, the problem with the high pressure developing is NOT from the filter.  Perhaps something has broken in the heater and has lodged itself either in the heater, or if you have a salt water chlorinator, something (the broken heater part?) may have gotten caught in the cell.

Does the flow seem to be the same as it was when you turned the pump on (just after moving the valve on the filter).  If so, then something is causing the pressure to rise in the filter.  

When you setup the filter,  Was the correct size AND type of sand used?  You cannot use any kind of sand.  It is specific to water filtration.  Typically, a silica sand with a size of #20 should be used.  Also, some sand filters require the use of pebble or gravel in the first couple of inches, then the rest is sand.

Also very important. DO NOT POUR THE SAND OR GRAVEL INTO A DRY TANK!!!  

You must put several inches of water into the tank before you begin to introduce the sand.  And continue to fill with water as you pour more sand in.  Failure to do so can break the laterals in the bottom of the tank!   If you filled the tank without water, the pump would begin to fill the tank from the top down.  The sand will begin to settle, and put increasing downward pressure on the laterals breaking them. The laterals at the base of the tank are what draw clean water away from the tank and hold back the filter media (sand).   If these become dislodged or broken, the sand can enter the laterals and block the manifold causing high pressure.  Then when you subsequently backwash, you flush those lines out and you would get semi good flow until the sand migrated back in though the broken lateral and once again cause high pressure..

 Your symptoms sound like this may have happened.  Are you getting some sand back into the pool?

[Erin54321]

Did you ever solve this problem. I have the same issue and couldn’t find any other blogs with this same problem. Thanks!