Sediment Filters for Well Water: Spin-Down, Cartridge, and Which Micron

First, look at what settles

Fill a glass or the bathtub and let it sit. Does sand drop to the bottom? That is Wisconsin’s first check for gritty water¹. What you see tells you the filter:

Particle sizes · USGS grade scale

Particle	Size	What it looks like	Filter
Sand	62.5 µm – 2 mm2	Grit that settles in seconds	Spin-down screen
Silt	4 – 62.5 µm2	Cloudy water that settles slowly	Cartridge
Clay	under 4 µm2	Milky water that stays cloudy	Fine cartridge or media filter; ask a pro

For mild cloudiness, Penn State suggests a cartridge filter; for severe cases, a multi-media filter³.

When the sand is a well problem

New sand, or more sand than before, usually means something changed in the well. Wisconsin’s natural resources department lists the causes: a well that was not properly developed, a larger pump, a sandstone formation crumbling into the well, or a screen that failed¹. The fixes are in the well: developing it, a liner, or a new screen. Sand is not a health risk, but it can shorten the life of appliances and damage the pump¹. Call a driller before you buy a filter to hide it.

Spin-down screens: for sand

A spin-down filter spins the water so sand drops into a clear bowl, and you flush it out through a valve at the bottom, with no downtime⁴. The screen sets the smallest particle it stops:

Spin-down screen sizes · Rusco product sheet

Mesh	Microns	Catches
30	533	Coarse sand
60	254	Medium sand
140	104	Fine sand
250	61	Very fine sand
1000	15	Coarse silt

Mesh sizes from Rusco⁴; the “catches” column compares them with the USGS sand sizes². Our take: start with the coarsest screen that stops your sand. A finer screen catches more but clogs faster: iSpring itself warns that its 50- and 100-micron screens can clog very quickly on water with a lot of sediment⁵.

Spin-down filter, screw-in

iSpring WSP Series Spin-Down (WSP-50 to WSP-1000)

No NSF/ANSI listing found

Screens

50, 100, 200, 500 or 1000 micron

Flow

up to 20 gpm (maker)

Pressure

15–115 psi

Ports

1 in. MNPT and 3/4 in. FNPT

Screen life

12–24 months (maker)

Strengths

• Same housing takes five screen sizes
• Flush valve and clear housing
• Threaded both ways, easy to install

Drawbacks

• The 50- and 100-micron screens clog fast on sandy water (maker's warning)
• Hard water can scale the screen
• Indoor use only, 40–100 °F

Good fit: a well with sand or grit that needs a cheap, flushable first stage.
Skip it if: silt or cloudy water: that needs a cartridge.

Spin-down filter, widest screen choice

Rusco 1 in. Spin-Down

No NSF/ANSI listing found

Screens

polyester 700 to 15 micron; stainless 500 to 75

Flow

1–25 gpm

Pressure

up to 150 psi

Ports

1 in. slip (PVC)

Strengths

• The widest range of screens we found
• Rated to 150 psi
• Flushes through a ball valve without shutting the water off

Drawbacks

• Slip ports: needs PVC solvent-welding or adapters
• Hand-tighten only: tools void the warranty
• Cold-water filter

Good fit: a DIY owner who wants to pick the exact screen for their sand.
Skip it if: you want a threaded, ready-to-install unit.

Cartridges: for silt and cloudy water

A cartridge traps particles in its depth, so it catches finer material but has to be replaced. Pentair says to change its whole-house cartridges every 3 to 6 months or less, and sooner if pressure at the tap drops noticeably or the taste, colour or flow changes⁶. No maker we checked gives a pressure number that means “change it now”, so watch the trend: a significant pressure drop can be the sign⁷.

20-inch cartridge housing

Pentair Pentek Big Blue 20 in. (150233)

No NSF/ANSI listing found

Cartridge

20 x 4.5 in., any micron rating

Flow

15 gpm; 1 psi drop when new

Max pressure

90 psi

Ports

1 in. FNPT

Strengths

• Takes standard Big Blue cartridges from many brands, from coarse to 5 micron
• Very low pressure drop when new
• Pressure-relief button for cartridge changes

Drawbacks

• Housing only: cartridge, wrench and bracket sold separately
• Its NSF/ANSI 42 listing covers the housing's strength, not what it filters
• Must be kept from freezing

Good fit: silt, cloudy water, or the 5-micron stage a UV system needs.
Skip it if: heavy sand: put a spin-down in front, or the cartridge clogs in days.

The common pairing on a sandy well: a spin-down first to take the sand, then a cartridge for what gets through. The spin-down protects the cartridge, and the cartridge protects everything after it.

Where it goes

Pentair says to install its filters after the water meter or pressure tank, with a shut-off valve before the filter⁶. The sediment stage usually comes first in the chain, to protect what follows: softeners and UV both have limits on cloudy water^8,9, and VIQUA says a 5-micron sediment filter must come before its UV units¹⁰.

1. Well pumpraw water
2. Sediment filtersand, silt
3. Iron filteriron, manganese, H₂Sif needed
4. Water softenerhardnessif needed
5. UV lightbacteriaif needed

What a sediment filter doesn’t do

It catches particles only. Dissolved iron, hardness and bacteria go straight through: in Health Canada’s survey of home units, sediment filters reduced hardness by a median of 0%¹¹. Pentair also warns not to use its filters on water that is microbiologically unsafe without disinfection before or after⁶.