Don't have cloudy water in your pool or high filter pressure? It's time to backwash. Backwashing is a routine swimming pool care process that allows your filtering system to function properly by ridding the system of accumulated dirt and debris. This book is an all-encompassing treatise on what, when, and why backwash your in-ground pool.
What Is Backwashing?
Backwashing pool is reversing the direction of water flow through your pool filter to flush out impurities and dirt. It's applied mostly on sand and DE (diatomaceous earth) filters. As particles get caught by your filter, it will no longer function as effectively—backwashing drains out the accumulation so your filter will function effectively once more.
Types of Filters That Require Backwashing
Sand Filters: Water passes over a sand bed that traps dirt. The sand clogs up over time and must be backwashed.
DE Filters: Employ a powder-coated grid to filter even smaller particles. These must also be backwashed with occasional reapplication of DE powder.
Cartridge filters are not backwashed but hand cleaned by you.
How Often to Backwash Your Pool?
- Depending on usage, filter type, and water quality. Some guidelines include:
- When the pressure gauge reads 8–10 psi above the clean baseline
- Every other 1–2 weeks of heavy use or the pollination season
- Following a major storm or algae treatment
More backwashing than required wastes water and filter media unnecessarily. Do so only as needed.
Step-by-Step Backwashing Procedure of a Pool Filter
Turn Off the Pump: Never ever make adjustments with the pump running.
Switch to "Backwash": Turn the multiport valve to backwash position.
Turn On the Pump: Rinse for 2–3 minutes or until water in the sight glass is free of any dirt.
Turn Off the Pump Again: Turn off during adjustments.
Set to "Rinse": This flushes out any remaining dirt and reconditions sand bed.
Run the Rinse Cycle: Let it run 30–60 seconds.
Set to "Filter": Return valve to normal operating position.
Restart the Pump: Check pressure and check for leaks.
Refer to manufacturer's instructions for your specific filter model for best results.
What You'll Need
- Multiport valve with the backwash setting
- Waste hose or specially designated drainage area
- DE powder (if using DE filters)
- Water to top off pool after backwashing
Backwashing removes water from your pool, so you'll need to top it up a little after that.
What You Need to Keep an Eye Out For That Tells You If Your Pool Must be Backwashed
- Unclear or muddy water
- Strained or poor return flow into the pool
- Filter gauge pressure increases
- Substandard vacuum
- Pull debris in pool while running filter
It can compromise circulation efficiency and support algae growth if left unchecked.
- Backwashing Secrets for Maximum Effectiveness
- Backwash during early morning time to prevent evaporation loss by the sun
- Implement a backwash sight glass in order to immediately know when water runs clean
- Log filter pressure to track when backwashing truly is needed
- Never backwash to a storm drain—local water discharge regulation must be observed
Post-Backwashing To-Do List
Top Off Water: Backfill with clean water to maintain levels.
Check Chemistry: Backwashing may disrupt water chemistry, so recheck pH and sanitizer levels.
Add DE Powder: In case you have a DE filter, recoat grids immediately after backwashing is finished.
Rinse Pool Deck: Any overflow or excess needs to be rinsed off in order to maintain your clean zone.
Backwashing Misconceptions and Mistakes to Avoid
Myth: You Have to Backwash Every Week, Regardless
Backwash only when necessary—waste too much water and reduces filter efficiency.
Faux pas: Forget to Rinse Cycle
Wash always after backwashing to prevent dirty water to circulate back into pool.
Myth: You Can Backwash Cartridge Filters
Cartridge filters have to be pulled out and rinsed out—backwashing is useless.
Faux pas: Not Checking Filter Pressure
Pressure gauge your filter operation best troubleshooting tool.
Backwashing a swimming pool isn't a chore—instead, it's one of the best methods of maintaining your pool in clean, healthy shape. Properly, your filtration system will be humming along and your water will be sparkling all summer long.
