New Filter, orJust a Backwash?

When the pressure gauge creeps up or the water loses its sparkle, plenty of pool owners assume the filter is finished. Most of the time it is not. It is just full, and a backwash will sort it out.

What backwashing actually does

A sand filter traps dirt as water passes through the sand bed. Over time that trapped dirt restricts flow, and the pressure gauge rises.

Backwashing reverses the flow through the filter, lifting the trapped dirt out of the sand and flushing it to waste. It takes a few minutes and restores the filter to normal working pressure.

When to backwash

• The pressure gauge reads well above its normal clean level
• Water flow from the return jets has dropped noticeably
• The water is cloudy even though your chemistry tests fine
• After vacuuming a dirty pool or heavy storm debris

Tip: note your gauge reading straight after a backwash. That is your clean baseline. When the needle climbs noticeably above it, backwash again.

How to backwash a sand filter

1. Turn the pump off. Never move the valve with the pump running.
2. Set the multiport valve to Backwash.
3. Turn the pump on and run until the water in the sight glass runs clear, usually two to three minutes.
4. Turn the pump off and set the valve to Rinse. Run for about 30 seconds to settle the sand.
5. Turn the pump off, return the valve to Filter and restart.

When the sand actually needs replacing

Filter sand does wear out. The grains slowly smooth over and stop grabbing fine dirt. The signs:

• Pressure climbs back up quickly after every backwash
• The water stays dull or cloudy despite balanced chemistry and regular backwashing
• Sand appears in the pool, which points to a cracked lateral inside the filter
• Backwashing has become a weekly job instead of an occasional one

Replacing the media or repairing a lateral is a routine job for us, and far cheaper than a whole new filter in most cases.

Cartridge filters are different

Cartridge filters cannot be backwashed. Instead, remove the cartridge and hose it down thoroughly between the pleats. Replace the cartridge when the fabric looks frayed, flattened or stays dirty after a proper clean.