A whole house sediment filter is the cheapest insurance in domestic water treatment and the stage most often undersized. Everything downstream benefits: the softener valve, the water heater, the washing machine solenoids, every tap cartridge and every later filtration stage. The only way to get it wrong is to fit a housing too small for the flow the house draws, and that happens constantly.
Where it goes and what it protects
The filter belongs at the point of entry, after the main shut off and before anything else in the treatment train, so that every stage after it sees water already free of grit. Sediment scores softener valve seals, settles in water heaters, jams the small solenoid valves in appliances, blocks aerators and shortens the life of every cartridge downstream by loading it with particles it was never meant to handle. Fitting the filter after a softener, which occasionally happens, protects the appliances and leaves the most expensive component exposed.
Size on flow, not on floor space
This is where installations fail. A standard slim housing has a modest flow rating, and a house running a shower, a washing machine and a kitchen tap together can exceed it easily, at which point the filter becomes a restriction and the pressure at the shower drops. A large diameter housing costs a little more, flows far better and holds much more dirt, so cartridges last longer as well. Work from the plausible simultaneous draw rather than the average, and where flow demand is high, two housings in parallel are a legitimate answer.
Cartridge or backwashing media
Cartridge housings are cheap, simple and suit light to moderate sediment. On heavy loads, typically a well carrying sand or silt, cartridges become a weekly chore and a backwashing media filter is the right answer, cleaning itself on a schedule instead of being thrown away. Between the two sits the spin down filter, a clear bowl with a screen that is flushed by opening a valve, which handles coarse sand well and is a useful first stage ahead of a cartridge on gritty water.
Installation details that save trouble later
Fit isolation valves either side and a bypass if the household cannot be without water during a cartridge change. Leave clearance below the housing equal to its own height, or the sump cannot be removed without dismantling the pipework. Support the housing on a bracket rather than letting the pipes carry the weight. Fit pressure gauges before and after if you want a real indicator of when to change the cartridge. Our whole house water filter guide covers combining this stage with carbon and softening in one train.
Questions people ask about sediment filter for house
Where should a whole house sediment filter be installed?
At the point of entry, after the main shut off and before the softener and every other treatment stage, so everything downstream is protected.
Why did my pressure drop after fitting one?
Almost always an undersized housing. Size on the peak simultaneous draw of the house, and prefer a large diameter housing over a slim one.
How often will the cartridge need changing?
It depends entirely on the sediment load. Gauges either side tell you honestly: a rising pressure difference across the filter is the signal.
When is a backwashing filter better than cartridges?
When the load is heavy enough that cartridges become a frequent chore, typically a well carrying sand or silt. It cleans itself instead of being replaced.