Sediment in well water

Best for

Homes with a steady amount of sand or fine grit, or that need to protect a softener, UV unit or carbon filter downstream.

Wrong fit

If sand appeared suddenly, the pump is cycling oddly or the water turned cloudy after rain, call a well contractor and test for bacteria first.

Tradeoff

A filter treats the symptom. If the well screen, casing or pump setting is the problem, sand will keep coming until the well is fixed.

What sediment looks like

Sediment is anything solid carried in your water. What it looks like tells you where it comes from:

A jar test helps. Fill a clear jar from a cold tap, let it stand, and watch. Sand drops to the bottom quickly, silt more slowly, and clay may stay suspended for a long time. Orange or black color that develops as the water sits is a dissolved metal oxidizing, not sediment from the well.

Is it a health risk?

Sand itself is mostly a plumbing nuisance: it clogs aerators and screens and fouls treatment equipment downstream. Cloudiness is a different matter. The EPA describes turbidity as a measure of cloudiness and notes that higher turbidity is often associated with higher levels of disease-causing microorganisms such as viruses, parasites and some bacteria. Cloudy water also makes disinfection less reliable, because particles block UV light.

So if your water turns cloudy, especially after rain or flooding, treat it as a possible bacteria problem until a coliform test says otherwise. See bacteria in well water.

When sediment means a well problem

Penn State Extension lists warning signs that a well or pump needs attention:

• Decreased pumping rate
• Decreased water level
• Increased sand or sediment content in the water (cloudiness)
• Decreased total well depth

If sand appeared suddenly, has been increasing, or comes with lower flow, a filter is the wrong first purchase. Penn State notes that problems are cheaper to fix early; a decrease of 25% or more in well yield generally means rehabilitation is in order. A licensed well contractor can check the screen, the pump setting and the casing. Penn State describes rehabilitation as chemical treatment or physical cleaning such as brushing, high-pressure jetting and surging.

Penn State lists the usual reasons a well starts pumping sediment:

• Improper well design, such as poor screen placement or slot size
• Too little development (pumping or surging to clear fine material) when the well was built
• Loss of the natural cementing that holds aquifer sand together
• Screen or casing corrosion
• Pumping the well beyond its design capacity

Corroded, enlarged screen holes let sand in, and that sand wears pump parts and enlarges the openings further. Penn State calls proper well development the most important way to prevent physical plugging. It also recommends keeping the well’s records, including the completion report with depth, construction and yield, past test results and contractor invoices, and having a well contractor inspect the well every ten years. An original yield figure is what lets you spot a 25% drop.

How to test

For most sediment problems, the jar test and a look at the well history tell you more than a lab. But order these if you have not tested recently:

• Iron and manganese, to rule out metal particles
• Turbidity, if the water is cloudy
• Total coliform bacteria, especially for cloudy water or a shallow, dug or bored well
• Hardness, if you plan to add a softener downstream

The guide to testing your well covers what to ask for.

How to size a sediment filter

Sediment filters are rated by the smallest particle they trap, in microns. NDSU Extension’s guidance:

Some context from UGA Extension: sand ranges from 50 microns to 2 millimeters, so even a 20 micron filter traps sand. Silt runs from 2 to 50 microns, and clay particles of about 0.2 to 2 microns are usually too small for typical cartridge filters. The trade-off is pressure and clogging. NDSU notes that 2 to 5 micron filters have smaller pores and need more pressure to push water through.

Placement matters. NDSU recommends that a whole-house sediment filter go right after the pressure tank on a private well, as the first piece of treatment equipment. The sediment filter guide compares cartridge, spin-down and backwashing options.

Cartridge types

UGA describes two basic designs. Depth cartridges have graded density, coarse outside and fine toward the core, trap particles inside the material and are usually inexpensive. Pleated cartridges have more surface area, so they handle more sediment before pressure drops, and UGA says they are less expensive in the long run despite a higher initial cost.

UGA also suggests a nonbiodegradable media, since bacteria can grow on paper (cellulose) filters, and a filter validated by NSF or the Water Quality Association.

Backwashing media filters

If cartridges clog too often, UGA says a backwashing media filter may be more economical. These are point-of-entry tanks with a 24 to 36 inch bed of silica sand, aluminum silicate or crushed anthracite that is cleaned by backflushing. Multimedia versions have more capacity, run at higher flow and need less frequent maintenance than single-media tanks.

Why it matters for other equipment

Sediment causes trouble for most equipment downstream:

• UV. Virginia Cooperative Extension says cloudy water or sediment limits UV light penetration, which is why UV is usually the last device, preceded by filtration. See UV systems for well water.
• Softeners. Penn State says turbid water can clog softener resin with mud and clay.
• Carbon filters. NDSU says activated carbon does not remove sediment well and clogs easily, so a sediment filter ahead of it extends its life.
• Reverse osmosis. Virginia Cooperative Extension notes a sediment prefilter is commonly used to protect the RO membrane.

Maintenance

• Replace or clean cartridges when you notice a drop in flow. UGA says this may be after several weeks or months.
• Watch the pressure gauges if your filter housing has them; a growing pressure drop means a loaded cartridge.
• Treat gallon ratings as rough guides, since the amount of sediment varies.
• If you are changing cartridges more and more often, the well may be getting worse. Call the contractor.
• After installation, UGA recommends testing both the raw and the treated water, then testing both every year and keeping a logbook of results and maintenance.

When to call a pro

Call a licensed well contractor if sand appears suddenly, if well output or water level drops, or after flooding. Call your local health department if cloudy water comes with a positive bacteria test. A plumber or water treatment professional can size and install a whole-house filter once the well is sound.