A sediment filter takes suspended solids out of water mechanically: sand, silt, rust flakes, clay and pipe scale that would otherwise clog aerators, score valve seats and blind the expensive filters downstream. It is the cheapest stage in any treatment train and the one that protects everything else. The choice comes down to three things: the type of housing, the micron rating, and whether you want to clean it or replace it.
Spin-down, cartridge or backwashing
A spin-down filter is a clear housing with a stainless screen and a flush valve at the bottom. It catches coarse grit, you open the valve to purge it, and it never needs a cartridge. A cartridge filter uses a replaceable pleated or wound element in a housing and goes finer, but it is a consumable. A backwashing media filter uses a bed of graded media in a tank with an automatic valve that reverses flow to rinse itself. Wells with heavy sand often use a spin-down ahead of a cartridge, so the cartridge lasts.
Micron ratings and the nominal versus absolute trap
The micron rating describes the size of particle the element is designed to stop. Coarser elements pass more water with less pressure drop and last longer; finer elements catch more but clog faster. The wrinkle is that a nominal rating means the element captures most particles of that size, while an absolute rating means it captures effectively all of them. Two elements with the same printed number can behave very differently, so read which word the manufacturer used before comparing them.
Staging coarse to fine beats one fine filter
Putting a single very fine cartridge on dirty water is a way to buy a lot of cartridges. Running a coarse element first and a finer one after it spreads the load: the first element takes the bulk of the sand and the second only has to polish. Pressure drop stays reasonable for longer and the total spend on replacements usually falls. Pleated elements can sometimes be rinsed and reused a time or two; spun elements generally cannot.
Know when it is spent
The honest indicator is pressure, not appearance. Fit gauges before and after the housing and change the element when the difference across it climbs, rather than on a guessed calendar. Falling shower pressure and a slow-filling toilet are the same signal arriving late. Install the housing with clearance below it to drop the sump, fit a bypass or at least shutoffs either side, and keep spare O-rings and a tub of silicone grease with the wrench. Our whole house filter maintenance guide covers the change routine.
Questions people ask about sediment filter
Does a sediment filter remove chemicals or hardness?
No. It is a mechanical strainer, so it only removes suspended particles. Dissolved contaminants such as hardness minerals, chlorine and metals pass straight through and need carbon, ion exchange or a membrane instead.
Where should a sediment filter be installed?
On the main line where water enters the house, ahead of every other treatment stage and before the water heater. On a well, put it after the pressure tank so the pump and tank are not fighting a clogged element.
How do I know which micron rating to choose?
Start coarse and work finer only if the water still carries visible particles. Very fine ratings on silty water cause frequent clogging and pressure loss, which is why staged coarse-then-fine setups are common on wells.
Can a sediment filter be cleaned instead of replaced?
Spin-down screens are designed to be flushed and reused indefinitely, and pleated cartridges tolerate a rinse once or twice. String-wound and melt-blown elements trap particles in their depth and should be replaced rather than washed.