Turn off your pump, switch the multiport valve to 'Backwash', run for 2-3 minutes until water clears, then switch to 'Rinse' for 30 seconds before returning to 'Filter' and adding fresh DE powder.
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Backwashing your DE filter is straightforward: turn off the pump, rotate the multiport valve to 'Backwash', run the pump for 2-3 minutes until the sight glass shows clear water, switch to 'Rinse' for 30 seconds, return to 'Filter', and add fresh diatomaceous earth through the skimmer. The entire process takes about 10 minutes and should be done when pressure rises 8-10 PSI above clean levels.
Before starting, check your pressure gauge reading. A DE filter needs backwashing when the pressure rises 8-10 PSI above the clean starting pressure. For most residential pools, this occurs every 4-6 weeks during normal operation, though heavy bather loads or algae blooms may require more frequent backwashing.
Safety first: Always turn off the pump before moving the multiport valve to prevent damage to the valve and potential injury from pressurized water lines.
After backwashing, your filter grids are clean but uncoated, providing minimal filtration until you add fresh DE. Calculate the correct amount based on your filter's square footage - typically 1 pound of DE per 10 square feet of filter area. Most residential DE filters require 4-8 pounds of DE powder.
Mix the DE powder in a bucket with pool water to create a slurry, then slowly pour it into the skimmer while the pump is running. This allows the DE to evenly coat the filter grids. Never add dry DE powder directly to the skimmer as it can clog the system.
Pressure rise is the primary indicator, but other signs include:
Avoid backwashing too frequently, as a slightly dirty filter actually works more effectively than a completely clean one. The initial DE cake helps trap finer particles.
If pressure remains high after backwashing, your filter grids likely need manual cleaning or replacement. Remove the grids and inspect for tears, permanent DE buildup, or oil contamination. Soak grids in a filter cleaner solution like Natural Chemistry Filter Perfect or muriatic acid solution (1 part acid to 20 parts water) to remove oils and mineral deposits.
Frequent backwashing indicates either poor water chemistry, excessive organic load, or damaged filter components. Test and balance your water chemistry first - maintain FC levels according to your CYA level using the FC/CYA chart, keep pH between 7.4-7.6, and ensure proper sanitizer residual.
If you see DE powder in your pool after adding fresh DE, you have torn or damaged filter grids that need replacement. This is a common issue in older filters or when grids haven't been properly maintained.
Between backwashes, maintain proper water chemistry to extend filter cycles. Keep your FC level appropriate for your CYA level - typically 2-4 ppm FC with 30-50 ppm CYA for most pools. Poor water balance forces your filter to work harder, shortening the time between backwashes.
Consider using a phosphate remover like Natural Chemistry PHOSfree if you're backwashing more frequently than every 3-4 weeks. High phosphate levels can feed algae growth, overwhelming your filtration system.
Schedule deep cleaning of your filter grids 2-3 times per season. Remove grids from the filter tank and clean with specialized filter cleaners to remove oils, lotions, and mineral deposits that regular backwashing can't eliminate.
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