Sediment Filter for Well Water: Spin-Down and Cartridge

For most wells, the best sediment setup is two stages. First comes a reusable spin-down screen that catches sand and grit and is cleaned by flushing. After it goes a cartridge filter around 5 microns that catches silt. The spin-down keeps the cartridge from clogging every few weeks, and the cartridge catches what the screen lets through. University of Nebraska–Lincoln (UNL) Extension’s rule of thumb is to use the largest rating that still removes what you need removed, because that needs the least maintenance.

The Rusco 1 in spin-down fits best if you want to choose a screen size for your sand. The SpringWell spin-down suits a fixed 90-micron first stage at high flow. For the fine stage, the SpringWell 5-micron canister suits busy households, and the Pentek Big Blue 20 suits buyers who want to pick their own cartridge.

Comparison table

Product	Type	Micron rating	Flow rate	Port size	Max pressure	Cleaning / replacement	Relative cost
Rusco 1 in Spin-Down	Spin-down screen	Polyester 15–700 µm; stainless 75–500 µm	1–25 gpm	1 in slip	150 psi	Reusable screen	Low ($)
SpringWell Spin-Down	Spin-down screen	90 µm	26.4 gpm max	1 in	Not stated	Reusable screen	Low ($)
SpringWell Canister + 5 Micron	Cartridge housing	5 µm	20 gpm (10 in); 35+ gpm (20 in)	1 in (10 in); 1.5 in (20 in)	Not stated	Replace cartridge; interval not stated	Low ($)
Pentek Big Blue 20 (150233)	Cartridge housing	Depends on cartridge (none included)	15 gpm	1 in female NPT	Not stated on product page	Replace cartridge; pressure-relief button	Low ($)

“Not stated” means the maker’s product page omits it. We don’t list prices.

Spin-down vs cartridge

A spin-down filter is a clear bowl with a cylindrical mesh screen. Incoming water swirls so heavier particles drop toward the bottom, and the screen catches the rest. Most are cleaned by opening a flush valve at the bottom of the bowl, so there is nothing to buy; check that the model you choose has one. Screens are coarse, from tens to hundreds of microns, so a spin-down catches sand and grit but not fine silt.

A cartridge filter pushes water through a wound, spun or pleated media. Virginia Tech Extension lists pleated paper, cellulose, wound string and spun polypropylene. It catches much finer particles, but it’s disposable and clogs faster the more it catches.

A third option, for heavy loads, is a backwashing sand filter. UGA Extension describes a tank with an 18 to 24 in bed of fine sand over gravel and recommends it for heavy particle loads, with a cartridge as a polishing stage. If you are changing cartridges weekly even behind a spin-down, that is the signal.

Micron staging: what each stage catches

UNL Extension gives typical particle sizes and notes that many filters are rated only to 20 microns, which may miss some silt:

Particle	Typical size (UNL)	Caught by a 90–150 µm spin-down?	Caught by a 5 µm cartridge?
Sand	50 µm to 2 mm	Most of it	Yes
Silt	2–50 µm	No	Most of it
Clay	0.2–2 µm	No	No; UNL points to microfiltration
“Flour sand” (very fine)	Too fine for many cartridges	No	Often not
Dissolved iron	Dissolved, not a particle	No	No, until oxidized

When comparing ratings, note two terms. UNL says a “nominal” rating should trap about 85 percent of particles at the rated size, and an “absolute” rating about 99.9 percent. If a UV unit comes later in your system, Ohio’s private water rule requires an absolute filter of no more than 5 microns ahead of it. A nominal 5-micron cartridge does not meet that. The UV filter roundup covers the rest of that stage.

A common sequence is a spin-down with a screen just fine enough to stop your sand, then a 20- to 5-micron cartridge, then any iron filter, softener or UV. The whole house water filters hub shows the full stage order.

Pressure drop and when to change cartridges

Every filter costs some pressure, and a loading cartridge costs more over time. UNL says flow is greatest when a cartridge is new and drops as trapped material builds up. It advises cleaning or replacing the cartridge when you notice a drop in flow. UNL also says to compare filters by the flow they deliver at household pressure, typically 30 psi, and that the manufacturer should give initial flow at a stated pressure. None of the four product pages here gives a pressure-drop curve, so treat the flow ratings as maximums.

Three ways to limit pressure loss:

• Go no finer than you need. A 1-micron cartridge on sandy water clogs quickly; UNL says too small a pore size or too much sediment means frequent replacement.
• Size up the housing. SpringWell’s 20 in canister is rated 35+ gpm against 20 gpm for its 10 in version, and longer cartridges have more surface to load.
• Install pressure gauges before and after the housing. A widening gap between them tells you the cartridge is loading before the shower does.

Change cartridges on schedule. UNL says bacteria can grow on filters, especially paper media, and suggests non-biodegradable media if that happens. The Minnesota Department of Health warns that unmaintained treatment units can make water quality worse.

The picks

Rusco 1 in Spin-Down: best fit for choosing a screen to match your sand

Rusco offers polyester screens from 15 to 700 microns (150 microns equals 100 mesh) and stainless steel screens from 75 to 500 microns. You pick the size for your grit. It’s rated 1 to 25 gpm and 150 psi, and the body is 11-3/8 in long by 5 in wide.

Cons, specifically:

• 1 in slip ports are solvent-weld (glued) connections, not threaded.
• The product page lists no temperature rating and no flush-valve details.

SpringWell Spin-Down: best fit for a high-flow, fixed coarse first stage

This one has a reusable 90-micron screen, a 26.4 gpm maximum flow and 1 in in/out ports. Warranty is lifetime against defects.

Cons, specifically:

• The product page lists only the 90-micron screen. If your sand is much finer, it will pass through.
• No pressure or temperature rating, and no flush instructions, on the page.

SpringWell Canister + 5 Micron: best fit for a fine second stage on a busy household

This is a cartridge housing with a 5-micron filter. The 10 in size is rated 20 gpm with 1 in ports, and the 20 in size is rated 35+ gpm with 1.5 in ports. It carries a lifetime warranty and a 6-month money-back guarantee.

Cons, specifically:

• SpringWell doesn’t say whether the 5-micron rating is nominal or absolute, so don’t count on it as the absolute 5-micron stage Ohio requires ahead of UV without confirmation.
• No cartridge material, pressure rating or change interval on the page.
• The 20 in version’s 1.5 in ports need reducers if your main line is 1 in.

Pentek Big Blue 20 (150233): best fit for buyers who want to pick their own 20 in cartridge

Pentair’s housing takes standard 20 in by 4.5 in heavy-duty cartridges. It is polypropylene, rated 15 gpm, with 1 in female NPT ports and a pressure-relief button on the cap for cartridge changes. It measures 7 by 7 by 21 in. Pentair aims it at households of 4 or more.

Cons, specifically:

• No cartridge in the box. Your micron rating, and whether it’s nominal or absolute, depends on what you buy.
• 15 gpm is the lowest flow here.
• The product page does not state a maximum pressure or temperature; check the spec sheet before installing near the top of your pressure switch range.

Who should skip all of these

• Water that turns orange after standing. That is dissolved iron oxidizing in the air. UNL says sediment filters catch iron only once it is insoluble, so you need oxidation first. See the iron filter roundup.
• Persistent cloudiness from clay or flour sand. UNL says these are too fine for typical cartridges and points to microfiltration.
• Sudden heavy sand from an established well. UGA lists a new well screen as part of the remedy for turbid water. A filter treats the symptom; have the well checked. New wells are different: UGA says initial cloudiness can clear with continued pumping.
• Cloudy water and bacteria concerns. UGA flags turbidity above 5 NTU as a reason to suspect contamination, and UNL says cartridge filters are not generally recommended for removing microbes. Test, then see the treatment system matrix and the well water filtration system roundup.

Sources

1. University of Nebraska–Lincoln Extension — Drinking Water Treatment, Sediment Filtration (G1492)
   Particle sizes for sand, silt and clay; nominal 85% vs absolute 99.9%; largest rating needs least maintenance; flow at 30 psi; replace on noticeable flow drop; limits
2. University of Georgia Extension — Water Quality and Common Treatments for Private Drinking Water Systems (B 939)
   Sand filter 18–24 in bed for heavy loads; cartridge for low turbidity; turbidity above 5 NTU; new well screen remedy; well development
3. Virginia Tech Extension — Household Water Treatment (442-670)
   Micron rating definition; cartridge media types; targets include oxidized iron and manganese
4. Ohio Administrative Code 3701-28-15
   Absolute filter of no more than 5 microns ahead of UV
5. Minnesota Department of Health — Home Water Treatment
   Unmaintained units lose effectiveness and can worsen water quality
6. Rusco — 1 in Spin-Down Filter
   Screen options, 1–25 gpm, 150 psi, 1 in slip
7. SpringWell — Spin-Down Sediment Filter
   90 micron reusable, 26.4 gpm, 1 in
8. SpringWell — Sediment Filter Canister + 5 Micron Filter
   10 in 20 gpm / 20 in 35+ gpm; 1 in / 1.5 in ports
9. Pentair — Pentek Big Blue 20 in Housing (150233)
   20 in x 4.5 in cartridges, 15 gpm, 1 in FNPT, pressure relief