It’s important to be sure all of your pool equipment is working properly and efficiently at all times. Following these steps will help you determine if your pool sand filter is working correctly or in need of replacement.
Does your pressure gauge reset to zero when your pump is off? If not, replace it.
Check is to see if there is water leaking from your backwash line while your pool sand filter is set to filter mode. If there is, chances are your multi-port gasket is worn and will need to be replaced. Through normal use, the gasket rubber will wear down and eventually allow water or debris to bypass the intended direction and escape out the backwash port (or return to the pool unfiltered).
Check to see if there is dirt or debris returning to your pool or during a pool vacuum. If there is, this can be a sign you have a broken lateral. Laterals are plastic parts at the bottom of the sand filter, with slits so small that it keeps out sand grains, until it cracks that is. It could also be a broken standpipe or diffuser.
Keep in mind of the age of your sand. If your pool is struggling to keep clear after a backwash, chances are your sand has reached its life expectancy of about 4-5 years. At this point, the sand loses its shape and starts to get full of oils and will clump up and become gunky. Another way to check for this would be another sign is your pressure gauge normal pressure remains high than it normally was low when you first installed your filter. If this occurs, you will need to replace the sand. It is a good measure to inspect your sand filters internal components at this time.