Pool Backwashing is the simple, powerful routine that keeps your pool water clear, your equipment running efficiently, and your swim season stress-free. If you’ve ever wondered why your filter pressure creeps up, why the water looks a bit dull, or why the pump seems to work harder than usual, you’re likely due for a backwash. Done correctly, this quick process flushes trapped debris from your filter media and restores flow—saving energy, extending equipment life, and improving water quality.
What is Pool Backwashing and Why It Matters
Backwashing is the process of reversing water flow through a pool filter to dislodge and remove dirt, oils, and fine particles. It’s used with sand and diatomaceous earth (DE) filters; cartridge filters are cleaned differently and do not get backwashed.
Here’s why it’s essential:
– Restores filter efficiency: Debris builds up and restricts flow, making your system work harder.
– Protects equipment: Lower strain on the pump and multiport valve reduces wear and tear.
– Improves water clarity: A clean filter captures more contaminants, keeping water sparkling.
– Saves time and money: Regular maintenance prevents larger, costlier problems down the line.
How Often Should You Backwash
– Pressure rule of thumb: When the filter pressure rises 8–10 psi above the clean “baseline” (record this after a full clean or backwash), it’s time to backwash.
– Usage and environment: Heavy swimmer load, storms, pollen, nearby landscaping, or new plaster can all increase frequency.
– Seasonal patterns: Expect more frequent backwashing during peak swim months; in off-season, monitor and backwash as needed.
Pool Backwashing: Step-by-Step for Sand Filters
1) Turn off the pump. Always start by switching off power to avoid damaging the multiport valve or filter internals.
2) Set the multiport valve to Backwash. Ensure the backwash hose is laid out and directed to a suitable drainage area, following local regulations.
3) Turn on the pump. Run 2–3 minutes or until the sight glass (if equipped) runs clear.
4) Turn off the pump and set to Rinse. Run for 20–30 seconds. Rinse settles the sand bed and clears plumbing so dirt doesn’t return to the pool.
5) Return to Filter. Turn the pump back on and confirm the pressure gauge has dropped close to the baseline.
6) Top up water. Backwashing lowers water level; refill to mid-skimmer.
Pro tip: Add a small amount of filter cleaner or clarifier before backwashing if oils are excessive, but follow manufacturer directions to avoid foaming or channeling in the sand bed.
Pool Backwashing: Step-by-Step for DE Filters
1) Turn off the pump. Ensure the system is safe to adjust.
2) Backwash as with sand filters. Set the valve to Backwash and run until water clears, then Rinse for 20–30 seconds, and return to Filter.
3) Recharge with fresh DE. This is crucial. After every DE backwash, measure and add the manufacturer-recommended amount of DE through the skimmer while the pump is running. Too little DE exposes grids and can damage them; too much reduces flow.
4) Monitor pressure. If pressure remains high after backwashing and recharging, perform a full teardown and clean the grids.
Note: Many DE filters benefit from an annual or semiannual deep clean and grid inspection. Replace torn grids and worn manifold parts promptly.
Filter Maintenance for Cartridge Systems
Cartridge filters don’t get backwashed. Instead:
– Turn off the pump and bleed pressure.
– Remove the cartridges and hose them off from top to bottom, spreading the pleats gently.
– Soak in a filter cleaner to remove oils and scale as needed.
– Rinse, reassemble, and record the clean pressure baseline.
Water Conservation and Environmental Tips
– Backwash only when needed. Use the pressure gauge, not a calendar.
– Install a separation tank for DE systems to capture media and prevent it from entering storm drains.
– Direct backwash water to an approved sanitary drain or dispersal area per local codes.
– Consider a glass or premium sand media upgrade for better filtration and potentially reduced backwash frequency.
Common Mistakes to Avoid
– Skipping the Rinse step: This can send dirty water right back into your pool.
– Backwashing too often: Overdoing it prevents the filter media from building a thin “dirt cake” that actually improves filtration. Follow the pressure gauge.
– Not recharging DE: Running without DE quickly damages grids.
– Ignoring high pressure after backwashing: Persistent high pressure indicates clogged media, channeling, or a need for a deep clean.
– Closing valves with the pump running: Always turn off power before moving the multiport handle to prevent seal damage.
– Using flocculants without understanding the aftermath: Floc can clog filters fast; be prepared for a thorough clean or vacuum-to-waste procedure.
Signs Your Filter Needs Attention Beyond Backwashing
– Pressure spikes immediately after cleaning: Internal channeling, broken laterals (sand), or damaged grids (DE) may be to blame.
– Cloudy water despite normal pressure: Chemistry imbalance (low sanitizer, high phosphates, poor pH) or undersized filter.
– Sand in the pool: A cracked lateral or standpipe in a sand filter needs repair.
– DE returning to the pool: Torn grids, mis-seated manifold, or missing o-rings.
Quick Chemistry Check for Better Results
– Maintain pH between 7.4–7.6, alkalinity between 80–120 ppm, and calcium hardness appropriate to your pool surface.
– Keep free chlorine within the recommended range for your sanitizer system.
– Use a clarifier sparingly when fine particles overwhelm filtration, and shock after heavy use or storms.
Simple Routine to Streamline Filter Maintenance
– Weekly: Check pressure gauge, skim basket, water level, and pump strainer.
– As needed: Backwash sand/DE at 8–10 psi above baseline; recharge DE immediately.
– Monthly: Inspect backwash hose, valve o-rings, and sight glass; clean cartridge filters if you use them.
– Seasonally: Deep clean filters, inspect media (replace sand every 5–7 years or sooner if channeled, grids as needed, cartridges every 2–3 years), and verify all gauges and valves are functioning.
Troubleshooting at a Glance
– High pressure, low return flow: Backwash or clean filter; check for clogged impeller or closed return valves.
– Air in pump basket after backwashing: Bleed air via filter air relief; inspect suction-side leaks at lid o-ring or unions.
– Milky water after backwash: Run Rinse longer, then Filter; verify DE dosage and distribution.
Safety First
– Always shut off power before moving the multiport valve handle or opening the filter.
– Wear eye and respiratory protection when handling DE powder and chemical cleaners.
– Relieve pressure via the air relief valve before removing any clamps or lids.
The Bottom Line
With a good pressure gauge, the right steps, and a little consistency, backwashing takes just a few minutes and pays off with clearer water, lower energy use, and longer equipment life. Treat it as part of a broader filter maintenance plan—tuning your chemistry, inspecting components, and performing periodic deep cleans—and you’ll enjoy a sparkling, effortlessly inviting pool all season long.
