Sediment Filters for Well Water: The Complete Guide

A sediment filter goes right after your well tank and before your first water treatment system. That is the whole answer to where it goes, and it is the same whether the next tank in line is an acid neutralizer, an iron filter or a softener. This page is the long version: the order every piece of equipment goes in, why nothing goes ahead of the pressure tank, how a cartridge and a spin-down screen actually stop sediment, and how to tell whether you need one when you already have a system.

Caller "Okay. So the Big Blue before the pressure tank?"

Aidan "No, after the pressure tank. This is all after."

A Florida caller this July, on an artesian well with a softener, about to add an iron filter. Everything below is the long version of that answer.

Where the sediment filter goes

Every filter goes after the well tank. The 5 micron Big Blue is first, your treatment tanks come next, and the Rusco spin-down screen goes last. Water comes up from the pump into the pressure tank, and everything that cleans it sits downstream of that tank on the line into the house.

The Big Blue goes right after the tank

The Big Blue mounts to the wall next to your well tank. If you are putting in an acid neutralizer, the Big Blue goes in first after the tank; water passes through the 5 micron cartridge inside, the cartridge traps the sediment, and then the water goes to the neutralizer and on to the rest of the house. I put it this way in the video below, and it is what I tell people on the phone. A caller in March with pH 6 water and 4 people in the house asked whether to run a spin-down as well as the Big Blue, and I told him to put the Big Blue first because it gives good flow rates and plenty of capacity, then the neutralizer, then the softener, then the spin-down, and his UV light last.

The cartridge is the filter here, not the blue housing. The 10 inch and 20 inch kits both ship with a 5 micron polyspun cartridge; which housing size fits your house is covered in the Big Blue housing guide, and which micron rating to run is covered in sediment filter micron ratings.

Why nothing goes before the pressure tank

A filter between the pump and the pressure tank puts the pressure switch on the wrong side of the filter. Boshart, a well-tank fitting manufacturer, spell out what happens: as the cartridge loads with sediment it clogs, the pump keeps pumping against the clog, and the switch, sitting after the filter, never sees that pressure and never tells the pump to shut off. Constant running at full pressure eventually destroys the pump and can damage the filter. Their conclusion is one line: sediment filters should always be installed after the pressure tank. The catalog for the Rusco we ship says the same thing: do not install it on the suction side of a pump.

On the phone I say it shorter. A Virginia caller in May with orange iron sediment asked about putting something ahead of his tank, and I told him you cannot put anything before the pressure tank because it slows the flow down and you get less pressure. The pressure tank also has to sit ahead of the treatment tanks, because a backwashing tank needs pressure to backwash.

The spin-down screen filter goes last

The Rusco spin-down we sell carries a 60 mesh screen, which Rusco rate at about 250 microns. That is 50 times coarser than the 5 micron cartridge, so it does a different job: it sits after the treatment tanks and catches any media the tanks let past, so it never reaches your plumbing. The March caller's Rusco went between his softener and his UV light. A city-water customer in January planning a softener asked whether he needed a screen at the end in case resin escaped, and I told him probably half of our customers put a spin-down after the system to trap anything. When you can see sediment in the clear bowl, you put a bucket under it, open the red-handled valve, and household pressure flushes it out in about 2 seconds.

How the screen itself works, the two sizes and what each mesh catches are in the spin-down filter guide. If the question is which type to buy rather than where it goes, read cartridge vs spin-down vs backwashing tank.

How a sediment filter works

A sediment filter is a strainer: water passes through a cartridge or a screen, and any particle bigger than the openings stays behind. Rusco put the rating this way: a 150 micron rated filter will not allow anything larger than 150 microns to pass through. That is all a sediment filter does. Dissolved iron, dissolved manganese, hardness, low pH, chlorine taste, bacteria and cysts are not mechanical sediment, and a sediment cartridge cannot remove them; those need the tank behind the filter.

Filter	How it stops sediment	How you clean it	Price
Big Blue cartridge filter (5 micron)	Water passes through the cartridge and the dirt stays in the cartridge. Pentek rate it 5 micron nominal from their own testing.	You replace the cartridge. Shut the water off, relieve the pressure, take the housing off with the wrench, drop in a new one. $45 for the 10 inch, $55 for the 20 inch.	$165 (10 inch kit), $195 (20 inch kit)
Rusco spin-down screen filter (flushes clean)	Water spins around a screen inside a clear bowl. The dirt drops to the bottom of the bowl where you can see it. The screen openings are about 250 microns (60 mesh).	Put a bucket under it, open the red-handled valve, and household pressure blows the sediment out in about 2 seconds. Nothing to buy.	$145 (1 inch), $249 (2 inch)
Backwashing sediment tank (rinses itself)	A tall tank, the same size as an acid neutralizer, filled with 2 cubic feet of Turbidex media. The media bed traps the dirt.	The Fleck 2510SXT valve backwashes the media and sends the dirt down a drain line. It needs a drain and an electrical outlet. Drain tubing is not included.	$1,895

Five microns is small. The average human hair is about 70 microns across, so the 5 micron cartridge is stopping particles 14 times smaller than a hair. That is why the 5 micron cartridge goes ahead of your equipment, and the coarser screen goes after it to catch media the tanks let past.

The backwashing tank is for the well where sediment is clogging the inlets to the faucets and the washing machine, the kind of load that has you changing a cartridge weekly. For a toilet tank with some dirt in it, a standard 5 micron cartridge is usually enough. I go through all three in the video.

Do you still need a sediment filter

Take the lid off the toilet tank in the bathroom you use most. If you see dirt and sediment in there, it is getting past your system, and you need a sediment filter ahead of it. That is the check I give people who ask whether they really need one when they already have a neutralizer or a softener.

Here is what happens without one. If you install an acid neutralizer with a fair amount of sediment in the water, that sediment gets into the neutralizer and works its way to the bottom over time. Then when you add more calcite, the new calcite compresses the sediment already in the tank and slows or shuts down your water flow. The same grit wears the control valve: a commercial customer in June with about 7 ppm iron asked whether the 5 micron cartridge would clog, and I told him we have found it is a good idea to trap the sediment before it gets into the head, so you get longer life out of the control valve.

If the sediment you are seeing is sand or grit at the tap, sand and sediment in well water covers what it means about the well itself. If the water is cloudy or milky rather than gritty, start with cloudy well water. Sizing by pump, flow and sediment kind is in how to choose a sediment filter, and how every other piece of equipment fits together is in the well water filtration guide.

Not sure where yours goes?

Text me a photo of your setup

Send a picture of the well tank and whatever is on the line now, and tell me what the water test shows. I will tell you what goes where and in what order.

Text Aidan443-277-2204 Call800-460-5810Aidan

8 AM to 5 PM Eastern, seven days a week. A real person, not a call center.

What buyers wrote after installing one

These are verified purchases from our store, written by the buyers, newest first. Reviewer names appear as the buyers wrote them.

Frequently asked questions