How to Measure a Pool or Spa Cartridge Filter
If you do not know the exact filter model or part number, measuring the existing cartridge is usually the easiest way to identify the correct replacement. You will need a few basic measurements, preferably in millimetres (mm).
Looking for the correct replacement filter?
Use our Filter Finder here to search by filter dimensions, model or cartridge number.
Measure as accurately as possible, but allow for a small amount of variation between an old cartridge and a new replacement. As a general guide, dimensions within approximately 5% may still indicate the same filter, particularly where an old cartridge or filter body has expanded, compressed or distorted with use.
1. Total length
Measure the main body length of the cartridge. Generally, do not include a handle, locating spigot or threaded connection unless the filter listing specifically requires that measurement.
2. Outside diameter
Measure straight across the widest part of the cartridge. This is the outside diameter of the filter.
3. Hole or spigot diameter
Spigot: If the cartridge has a male locating spigot or male threaded connection, measure the outside diameter of the spigot or thread.
Hole: If the cartridge has an open hole rather than a spigot, measure the inside diameter of the hole.
4. End connection type
The end connection is just as important as the overall dimensions. Common cartridge filter connections include:
- Open hole
- Fine thread
- Coarse thread
- Male spigot
- Camlock or bayonet-style fitting
Before ordering, check all four:
- Overall cartridge length
- Outside diameter
- Hole or spigot diameter
- End connection or thread type
Still unsure? Use our Filter Finder to narrow down the correct replacement from your measurements.
