When should I backwash my filter?

Pool Parts To Go

Backwashing at the right time keeps your pool water clear and protects your equipment. That said, the right time for your system will most likely vary compared to your neighbors'. There are multiple factors that determine when your system needs to be backwashed. Don’t worry, though, we are here to help you figure out when is best for your setup.

The Short Answer

You should backwash your pool filter when the pressure gauge reads 8–10 PSI higher than its normal (clean) pressure. There is no set number, as most pools will have different regular readings.

How to Tell It’s Time to Backwash

Here are the most reliable signs:

  • Rising pressure on the gauge
     After cleaning or installing your filter, note the “clean” PSI. When it climbs 8–10 PSI above that number, it’s time.

  • Cloudy water or weaker circulation
     If your returns feel sluggish or the filter isn’t clearing as well as you think it should, the filter may be clogged.

  • After heavy use or a big mess
     Pool party, storm, or algae cleanup? Your filter is working overtime and may need backwashing sooner than expected.

Filter Type Matters

Backwashing applies mainly to sand and DE filters:

  • Sand filters – Backwash when pressure rises, typically every 2–4 weeks, depending on usage.

  • DE filters – Backwash when pressure rises, then add fresh DE afterward to maintain proper filtration.

  • Cartridge filters – These are not backwashed. Instead, remove and rinse the cartridges when the pressure rises 8–10 PSI.

Pro Tip 

Don’t backwash too often. A slightly dirty sand filter actually traps tiny particles better than a freshly backwashed one. Think of it like coffee grounds settling into a better filter bed.

Why Backwashing Matters

  • Restores proper water flow

  • Reduces strain on your pool pump

  • Improves filtration efficiency

  • Helps extend the life of your filter system

Keeping an eye on your pressure gauge is one of the easiest ways to stay ahead of pool problems—and your filter will thank you for it. Still have questions? Don’t worry! At PoolPartsToGo, we are happy to answer any questions you may have!