Filter housings
The canister the cartridge sits in. Standard sizes make cartridges interchangeable; proprietary ones do not.
A filter housing is a pressure vessel with a lid: an inlet, an outlet, a cartridge inside and an O-ring keeping the mains out of your cupboard. Simple, and worth choosing carefully because it determines your consumable costs for as long as you own it.
The sizes that matter are 10 x 2.5 and 20 x 2.5 for point-of-use, and 10 x 4.5 and 20 x 4.5 — often called big blue — for whole-house work where flow rate matters. Any cartridge built to the same standard will fit.
Two features are worth paying for. A clear bowl, so you can see the cartridge's condition rather than guessing. And a pressure release button, so you are not fighting a housing holding several bar of mains pressure when you try to open it.
Best for
- Building a filtration system to your own specification
- Replacing a cracked or crazed housing
- Escaping a proprietary cartridge system
- Adding a stage to an existing setup
Larger housings and stainless versions available for commercial flow rates and pressures.
Pros and cons
Pros
- Standard sizes mean genuine cartridge competition
- Clear bowls make maintenance visual
- Modular — stages can be added as needed
- Long service life; only the O-ring is really consumable
Cons
- Needs a bracket and proper mounting, not just hanging on the pipe
- O-rings must be greased or the housing seizes
- Cheap housings crack, and they crack under mains pressure
- Ports come in different thread sizes
Can you install it yourself?
Yes, this is a realistic DIY job
Skill level: Moderate · Time: about 1.5 hours
Mount the bracket to something solid — a full 20 x 4.5 housing is heavy — fit isolation valves either side, connect, and pressure test before walking away.
Tools you will need
- Wall bracket and fixings
- Pipe cutter
- PTFE tape
- Isolation valves
- Housing spanner
Call a plumber if
- It is going on the rising main
Maintenance
Replace the O-ring annually, grease it at every cartridge change.
What installation costs
£100–£250 indicative UK labour
Labour only, for a housing on an accessible line.
