Backwashing your sand filter is a regular part of pool maintenance, but are you doing it too often? As your sand filter works, it traps dirt and other particles in the space between sand grains. As those spaces fill up they get better at catching smaller particles, meaning a slightly dirty filter can filter out material that a clean filter cannot. If you backwash on a set schedule, you may be doing it before your filter reaches this point.

So when should you backwash your filter? If you have pressure gauges on both the inlet and outlet of your filter, you should backwash when the pressure difference between the two reaches 10 to 20 psi. If you only have a single pressure gauge on your filter, then you'll want to backwash when your pressure reaches 8 to 10 psi higher than what its pressure is after a fresh backwash. Be sure to have that baseline pressure level marked or use the adjustable START / CLEAN FILTER pressure gauge cover to mark what your clean filter pressure level is.