Filter service

When you need it

• The pressure gauge reads well above its clean starting level.
• Pressure stays high even after backwashing.
• The water is cloudy although the chemistry is right.
• Sand or debris is returning to the pool.
• Leaks at the multiport valve, tank clamp or drain plug.

How a specialist does it

Cartridge filters. Pentair's Clean & Clear Plus manual says to clean the filter when the gauge reads 8 to 10 psi higher than the original starting pressure. Cartridges are removed and hosed inside and out. Before the tank is opened, the manual requires the pump and any automatic controls to be switched off, the air relief valve opened, and a wait until the gauge reads zero. It warns that the lid can blow off on restart if the clamp is not assembled correctly, and recommends checking clamp tension at least once a month.

Sand filters. Hayward's guidance on filters that stay at high pressure after backwashing lists several causes:

• a sand bed clogged with mineral deposits that will not backwash away, sometimes from calcium-based chlorine or other sanitisers
• a closed or partly closed valve on the return
• a pump that is too small: Hayward says that if the pump supplies less than 60% of the filter's designed flow rate, the filter will never backwash completely
• a pump that is too large, exceeding the filter's maximum flow and causing the sand bed to channel so debris bypasses filtration

Before changing all the sand, Hayward suggests removing about an inch of the top layer and replacing it with the same amount, then trying a filter cleaner.

A full service usually covers the condition of the media or cartridge, wear on valves and gaskets, the gauge and air relief valve, and a check that pump and filter are correctly matched.

What to ask before you hire

• What was the clean starting pressure, and what is it now?
• Is the problem the media, the valve, or a mismatch between pump and filter?
• Will you replace sand or cartridges, and with what?
• How will old media and backwash water be disposed of?
• Will you check and record the clamp, O-rings and air relief valve?
• How often should my filter be serviced, given how the pool is used?

UAE notes

Abu Dhabi's guide to the swimming pool regulations, which covers pools other than private villas, requires filters to be maintained periodically and cleaned at least once a week. Hotels and shared pools in Abu Dhabi should check that their maintenance contract covers that interval and keeps records.

After dusty or windy spells, watch the pressure gauge more closely, since airborne dust ends up in the pool and then in the filter.

If a new, larger pump has recently been fitted and filter problems started afterwards, mention it. The mismatch Hayward describes is easy to create during an upgrade and easy to miss.

Keep the filter's label or manual. Maximum and minimum flow rates are printed there, and a technician needs them to check the pump and filter are compatible.