How it connects
The cartridge end cap with an elastomeric flat gasket is pressed axially against a raised knife-edge ridge or circular seat inside the housing as the housing bowl is threaded or clamped shut.
Male and female halves
Female end cap bore / flat face gasket that receives the male locating spigot / post and knife-edge compression seat of the housing.
Usually connects to
- housing sump knife-edge seat
- housing head knife-edge / post seat
- housing center post / spigot
Common sizes
- Typically ~1" to 1.1" (25-28 mm) internal bore ID, ~1.8" to 2.2" (45-56 mm) gasket OD; for 2.5" and 4.5" (Big Blue) diameter filter cartridges in 10" and 20" lengths.
Where it is used
residential water filtrationcommercial water treatmentindustrial process pre-filtrationreverse osmosis pre-filtration
Variations
- DOE (double open end with flat gaskets on both ends)
- SOE (single open end with one flat gasket and one closed blind cap)
- integrated molded plastisol/Santoprene end caps with integral sealing lips
How to recognise it
Look for a flat, unthreaded end cap on a cylindrical filter cartridge with a central through-hole surrounded by an annular flat rubber or silicone gasket ring.
Often confused with
| Confused with | How to tell them apart |
|---|---|
| Code 3 (222 O-ring) cartridge end | Code 3 uses two external radial O-rings on an extended male spigot instead of a flat face compression gasket. |
| Code 7 (226 bayonet) cartridge end | Code 7 features twin O-rings and two locking bayonet tabs rather than a flat unthreaded drop-in gasket face. |
Also called
DOE flat gasket end capfilter cartridge DOE endknife-edge flat gasket sealdrop-in cartridge end seal
Good to know
Standard drop-in water filter interface used in standard 10-inch and 20-inch filter housings (such as Pentair/Pentek, GE, Culligan, and generic 2.5" and 4.5" sumps).
Design with real parts
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