The filter keeps pool water clear by trapping debris as water circulates. Choosing one means picking a filter type and a size that suit your pool and your pump, and understanding the upkeep each type needs. This guide walks through those decisions.
The three common filter types
- Cartridge filters trap debris in pleated fabric cartridges. They are cleaned by removing and rinsing the cartridges, so there is no backwashing. Cartridges are eventually replaced.
- Sand filters pass water through a bed of filter media. They are cleaned by backwashing, which reverses the flow and sends debris to waste. The media is replaced periodically.
- DE filters use grids coated with diatomaceous earth (DE) powder. They are backwashed or cleaned, then recharged with fresh DE according to the manufacturer's instructions.
Each type can keep a pool clear when it is sized correctly and maintained. The right choice depends on your pool, your plumbing and how you prefer to handle maintenance.
How filters are sized
Manufacturers publish a few numbers that matter when comparing filters:
- Filter area, usually in square feet. A larger area generally means more capacity to hold debris between cleanings.
- Maximum or design flow rate, in gallons per minute (gpm). The pump's flow should stay within the filter's rating.
- Turnover capacity, the number of gallons the filter can process in a set time. Many spec sheets list it for 6-hour and 8-hour turnovers.
Start from your pool and spa volume and your pump's flow, then compare filters whose ratings cover them. If your pool gets heavy debris from trees or frequent use, extra filter area can mean fewer cleanings. Always check the manufacturer's specification sheet for the exact model.
Fit on the equipment pad
- Plumbing size and connection type should match your existing pipes and valves.
- Clearance: tall cartridge filters need room above the tank to lift cartridges out. Check the manufacturer's clearance figure.
- Drainage: backwashing filters need an approved place to discharge water. Local rules can limit where backwash water may go.
- Pump match: a new variable-speed pump and an old filter should still be compatible. Our pump repair-or-replace guide covers what to check on the pump side.
Maintenance to plan for
A pressure gauge on the filter is the usual guide to cleaning. Note the pressure after a cleaning, and clean again when it rises by the amount your filter's manual specifies. Some filters also include a clean/dirty indicator. Plan for:
- Cartridge rinsing and periodic cartridge replacement.
- Backwashing and periodic media replacement for sand filters.
- Backwashing or cleaning and DE recharge for DE filters.
- Checking O-rings, lids and air-relief valves during cleanings.
Filter selection checklist
- Pool and spa volume in gallons
- Your pump's brand, model and flow
- Current filter brand, model and size (from the label)
- Pipe size and available space on the pad
- Preferred maintenance: rinsing cartridges or backwashing
- Any local rules on backwash discharge
Get help choosing
To match a filter to your pump and pool, send us your current equipment details. If you would rather have the filter cleaned and monitored for you, see Showtime Pools' weekly pool maintenance service. Installation and local delivery coverage depend on your address, so please confirm availability with our team before you order.