Spin-Down Sediment Filter for Well Water: How It Works & When You Need One

A spin-down sediment filter is the white inline filter with the clear bowl and the red valve on the bottom. Water spins inside the bowl, sand and grit drop to the bottom, and when the bowl fills you put a bucket under it, open the valve, and 2 seconds of household water pressure flushes it clean. No cartridges to change. No media to replace. Open a valve, flush the sediment, and you're done in seconds. This page is the long version of what I tell people who call confused about which spin-down to buy, where it goes, what it catches, and whether it replaces the Big Blue.

Caller "I'm kinda confused. I'm trying to research it here, and I thought just a spin down was a spin down, but apparently there's different types of spin downs, right?"

Aidan "We use the Rusco with the mesh inside. It's fairly priced. It's easy to maintain. There's some that have stainless steel inside. We don't sell those. And there's some that people claim are self backwashing. We just use the basic Rusco. It gets filled with sediment, you put a bucket under it, open the valve, the household pressure flushes it out in, like, 2 seconds, and you're done."

A caller in July with sediment collecting in his toilet tank, sorting through listings before he hired a plumber. This page is the long version of that answer.

What a spin-down catches

The Rusco we sell ships with a 60 mesh polyester screen, about 250 microns. Sand, grit and rust flakes stay in the bowl. Finer sediment and dissolved iron pass straight through. It uses centrifugal force. It spins the water around and forces the sediment to the bottom of the collection chamber, and the screen holds anything bigger than its opening. You can see the bowl fill, which is the whole point of the clear housing: you flush when it looks dirty, not on a calendar.

On the phone I put it this way: it gets all the big, medium and large chunks of sediment, and it doesn't filter down to as small a particle as the Big Blue. If you have sand or grit at the tap, the 5 micron Big Blue after the well tank is the first filter, and this screen at the end of the line is the backstop. If your water is cloudy or milky, a spin-down is not the tool: it does not filter down to as small a particle as the Big Blue, and the cloudy water guide covers what does. And if the problem is iron, a spin-down does nothing for it: iron is dissolved in the water, and you have to precipitate it out with an iron filter before anything can strain it.

Rusco makes the screen in 24, 30, 40, 60, 100, 140, 250, 500 and 1000 mesh, which is 700 microns down to 15 microns, and they all fit the same housing. Two kinds of spin-down we do not sell: the ones with a stainless steel screen inside, and the ones sold as self-backwashing, which customers who bought them elsewhere tell me do not work that well.

Here I show where the Rusco spin-down fits next to Big Blue cartridge and backwashing sediment filters. The Rusco part starts at 1:09.

Where the spin-down goes

Every filter goes after the well tank, and the order is fixed. The 5 micron Big Blue is first in line after the pressure tank, the treatment tanks come next, and the Rusco spin-down goes at the end of the line, right before the house. The Big Blue keeps silt and sand out of the neutralizer, iron filter, softener and UV. The spin-down at the end catches what those tanks can let past: calcite fines, resin beads, carbon. If something goes wrong in a tank and media gets heaved out, the spin-down catches it and keeps it from getting into your plumbing.

Nothing goes between the pump and the tank. The spec sheet for this filter says not to install a filter with a purge valve on the suction side of a pump, and every filter we sell goes after the well tank. In February a caller's plumber had piped the neutralizer and then the spin-down, with nothing ahead of the neutralizer. The spin-down was in the right place; what was missing was the 5 micron cartridge filter between the pressure tank and the neutralizer, to keep sediment out of the tank. For how a sediment filter works and where it goes in the train in more detail, the complete guide covers the whole line.

Standard 1 inch or Large 2 inch

The Standard 1 inch Rusco ($145) is rated 1 to 25 gallons a minute and fits 3/4 and 1 inch plumbing. The Large 2 inch ($249) is rated 18 to 100 gallons a minute, and it needs at least 18 gallons a minute before the water spins. Both ship with the same 60 mesh screen and the same red flush valve. The Large is 6 1/2 inches longer, and its 2 inch ports reduce down to whatever size you need: 1.5 inch, 1.25 inch, 1 inch, 3/4 inch.

The spec sheet sizes these by flow, not by pipe, and says the size of the pipe in your system may not be the best indicator. It also says the spin-out separation is best at the highest flow rates, and the 2 inch model needs 18 gallons a minute before it does its spinning at all. Below that the mesh still strains what passes through it, but you have bought a bigger housing, not a better filter. If your pump and plumbing move more than 25 gallons a minute, or your main is 1.5 or 2 inch, that is the Large. Otherwise it is the Standard. If you want the flow math for your pump, the guide on sizing a sediment filter by pump and flow walks through it.

Not sure which size to buy

Text me a photo of the line

Send a photo of the line coming off your pressure tank and tell me what the sediment looks like. I will tell you Standard or Large, and whether a cartridge filter belongs behind it.

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

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

When you still need a cartridge filter

There is no 5 micron spin-down screen. The finest screen Rusco makes is 1000 mesh, about 15 microns. The fine work belongs to a 5 micron Big Blue cartridge filter right after the well tank, and the spin-down at the end of the line is the backstop. A spin-down is never your only filter on a well with treatment tanks. The Big Blue up front stops the silt and sand before it reaches the valves, and the spin-down behind the tanks stops the media they let past. Callers ask me whether they need the spin-down, the Big Blue, or both: if you have treatment tanks, both. The Rusco comes with a 60 mesh screen, and you leave that the way it is; the Big Blue comes with a 5 micron and takes out the small stuff.

Can you skip the Big Blue and just buy a finer spin-down screen? You can, and we stock the 1000 mesh screen for the Large Rusco at $125 for people who want to. But a screen that fine still does not reach 5 microns. A 10 inch Big Blue kit is $165 and a 20 inch is $195, with the 5 micron cartridge in the housing. The Big Blue housings and cartridges guide covers which one, and the guide to which micron rating to run covers the 5 versus 20 question. If sediment is heavy enough to clog the inlets to your faucets and washing machine, that is when a backwashing sediment filter ($1,895) comes in; the cartridge vs spin-down vs backwashing comparison lays out where each one wins.

How to flush a spin-down filter

You see sediment build up in the collection chamber, you put a bucket underneath of it, open the red-handled valve, and your household water pressure blows it out in about 2 seconds. No tools, no shutoff, no cartridge. How often depends on how much sediment your well sends; the clear bowl tells you.

1. Look at the clear bowl

   Sediment collects in the bottom of the bowl below the screen. When there is a visible layer, it is time. You do not need to shut the water off.

2. Put a bucket under the red valve

   The flush comes out with the full pressure of your system. A bucket works; a short piece of hose from the valve to a floor drain or sump pit works better, and one buyer wrote that he wished he had known that before the first flush.

3. Open the red-handled valve

   Turn the handle. Household pressure pushes the sediment out of the bottom of the bowl. About 2 seconds.

4. Close it

   Turn the handle back. The filter is back in service; there is nothing to reset or replace. If the screen itself ever looks coated, the bowl unscrews and the polyester screen rinses clean and goes back in.

What your plumber needs to know

The Rusco mounts straight up and down with the clear bowl pointing at the floor, at the end of the line after the treatment tanks, on the cold water line. The pipe holds it up: no bracket, no wall mount. It cannot go sideways or upside down, because the sediment has to fall to the bottom of the collection chamber for the spin to work. It is light, nothing like a Big Blue housing that weighs 10 or 15 pounds.

The Standard has 1 inch ports. If your line is 3/4 inch, you reduce down with a bushing in the fitting that connects the filter to the plumbing. If you have 1 inch plumbing you are good to go; you may need to convert from PVC to a CPVC fitting to make the connection. The Large has 2 inch ports and reduces the same way. Rusco rates the housing for cold water at 150 PSI. We recommend a licensed plumber for the install, and we will walk your plumber through the placement by phone at 800-460-5810. The how to install a sediment filter guide has the full sequence, with the Big Blue alongside it.

One honest note from a buyer in May, who put a Large Rusco ahead of a new iron filter: it was in a tight space with two kinds of fittings, and it took longer than the couple of hours he expected. Plan the spot before the pipe is cut. You will be looking at the bowl and reaching the valve for years, so leave room for both.

What buyers wrote after installing one

These are verified purchases from our store, newest first, as written.

Frequently asked questions