Whole house sediment filters catch the solid material carried in your supply: sand, silt, rust flakes, scale chips and the fine grit that shows up in aerators. They are the cheapest stage in any treatment train and the one that protects everything downstream, because grit that reaches a softener or a carbon tank shortens the life of media that costs far more than a cartridge.
The three families you are choosing between
Spin down filters use a stainless steel screen in a clear housing and are flushed by opening a valve at the bottom, so nothing is consumed and nothing is thrown away. They handle coarse sand well and fine silt poorly. Cartridge filters use a replaceable element in a housing, either pleated, spun polypropylene or string wound, and are the common choice for household lines because they are inexpensive and available in many ratings. Backwashing tank filters hold a bed of graded media and clean themselves on a schedule by reversing flow to a drain, which suits heavy loads and houses where nobody wants to change a cartridge every few weeks. Cost, maintenance appetite and how dirty the water really is decide which family fits.
Micron ratings and the nominal trap
A micron rating describes the size of particle the element is meant to stop, and a smaller number is not automatically better. Most household cartridges are nominal rather than absolute, meaning they capture most particles at the stated size rather than all of them, so two cartridges with the same printed rating can perform differently. Fitting a very fine element to water that carries a lot of sand simply means the cartridge blinds off in days and your pressure collapses. The usual arrangement is staged: a coarse element or spin down screen first to take the bulk, then a finer element behind it to polish. That way the cheap stage does the heavy work and the fine stage lasts.
Sizing so the pressure survives
Sediment filtration is where whole house pressure is usually lost, and it is lost twice: once to the housing itself and again as the element loads with dirt. Bigger housings hold more surface area, so they clog more slowly and restrict less at the same flow. That is why the large diameter housings are standard on main lines while the slim ten inch housings belong on a single appliance or a branch. Check the port size too, since a housing plumbed with undersized connections throttles the whole house regardless of the cartridge inside. A pressure gauge before and after the filter turns cartridge changes from guesswork into a reading you can watch.
Where it sits and what it cannot do
The sediment stage goes first, right after the main shutoff and any pressure regulator, ahead of the softener, the carbon tank and any ultraviolet lamp. Put a bypass and isolation valves around it so a cartridge change does not mean shutting the house down. Understand its limit clearly: a sediment filter removes suspended solids and nothing else. Dissolved iron, hardness, chlorine, nitrate and bacteria all pass through untouched, and cloudy water that clears when it stands is dissolved gas rather than sediment. If your complaint is staining, smell or a failed bacteria test, the sediment filter is the stage that protects the real fix rather than being it.
Questions people ask about whole house sediment filters
How often should a sediment cartridge be changed?
Change it on pressure drop rather than on the calendar. Fit gauges either side, note the difference when the cartridge is new, and swap it when that gap has roughly doubled or when flow at the fixtures noticeably falls.
Is a washable pleated cartridge worth it?
Sometimes. Pleated elements can be rinsed and reused a few times when the load is sand rather than silt, but they never recover fully, and organic fouling cannot be washed out at all.
Do I need a sediment filter on city water?
Often yes, in a modest rating. Mains work, hydrant flushing and old iron pipe all release particles, and a filter ahead of a softener or carbon tank protects media that is expensive to replace.
Can a sediment filter remove rust color from my water?
Only if the rust is already an oxidized particle. Clear water that turns orange after standing is carrying dissolved iron, which needs an oxidizing filter or a softener within its limits rather than a sediment cartridge.