A whole house sediment water filter catches the sand, silt, rust and scale flakes travelling in your main line before they reach fixtures, appliances and the rest of your treatment equipment. It is the first stage in almost every system, and choosing one is a trade between how fine it filters and how often you service it.
The three types you will choose between
A spin down separator uses a clear housing and a screen, catching coarse sand and grit, and is flushed by opening a valve at the bottom rather than replacing anything. A cartridge filter uses a replaceable pleated or spun element in a housing, filters much finer, and is the common household choice. A backwashing media tank holds a graded bed and cleans itself to drain on a schedule, handling heavy sediment loads with high flow and low pressure drop, at the cost of needing a drain, an outlet and floor space.
Rating: finer is not automatically better
Cartridges are rated by the particle size they hold back, and a nominal rating means most particles of that size are caught while an absolute rating is a stricter guarantee. A very fine cartridge on water carrying heavy silt will blind in days, taking your pressure with it. The usual approach on well water is staging: a coarse stage first, then a finer one behind it, so the cheap element does the bulk work and the fine element lasts. Pleated cartridges present more surface area than spun ones and last longer on the same water.
Watching pressure instead of the calendar
Fit a pressure gauge before and after the filter housing. The difference between them is the honest measure of how loaded the cartridge is, and it turns a guess into a decision. Rising differential means the element is filling; a sudden change means something upstream has shifted, such as a pump pulling sand after the water table dropped. Sizing matters here too, since an undersized housing shows a differential from the day it is fitted. Manufacturers publish flow ratings and micron options for exactly this comparison.
Where it goes and what it protects
The sediment filter goes on the main line where water enters, after the pressure tank on a well or after the meter on city water, and ahead of every other treatment stage. That position is deliberate: sediment fouls softener resin, blinds carbon beds, scratches valve seats and ruins reverse osmosis membranes, so the cheapest element in the system protects the most expensive ones. Fit isolation valves and a bypass so cartridges can be changed without shutting off the building, and leave clearance below the housing to drop the sump.
What it will not do
A sediment filter removes suspended solids only. Dissolved iron passes straight through and stains later, hardness passes through and scales, chlorine passes through, and nitrate and other dissolved contaminants are untouched. If a sediment cartridge turns orange quickly, that is oxidized iron, and the answer is an iron filter upstream rather than a finer sediment element. Our whole house water filter comparison covers building the rest of the train once sediment is handled, which is the point where most well systems get their sequence right or wrong.
Questions people ask about whole house sediment water filter
What micron rating should a whole house sediment filter be?
It depends on your water. Coarse ratings suit heavy sand and last longer, fine ratings catch silt but block sooner. Staging a coarse element ahead of a fine one is the usual compromise.
How often should the cartridge be changed?
When the pressure differential across the housing rises, which is why gauges are worth fitting. On clean city water that can be months; on a sandy well it can be weeks.
Will a sediment filter remove iron staining?
Only iron that is already oxidized into particles, and it will clog fast doing it. Dissolved iron needs an oxidizing iron filter, not a sediment cartridge.
Does a sediment filter reduce water pressure?
A correctly sized clean filter costs very little pressure. A noticeable drop means the element is loaded, the rating is too fine for the water, or the housing is too small for the flow.