Sediment and Sand in Well Water

First, figure out what's in the water

Fill a clear glass from the cold tap and let it sit for a few minutes. What you see tells you where to look:

That last row is the one to take seriously. If water clouds up after rain, surface water may be getting past the well cap or casing, and it can carry bacteria with it. EPA and the CDC both say to test when the water's color, taste or smell changes and after flooding. See coliform bacteria in well water.

Why a well starts making sand

Boshart, which makes well and pump fittings, lists the usual causes:

• The pump is set too low. A submersible near the bottom of the well pulls in sediment, and in older wells sand builds up until it reaches the intake.
• The pump is too big. A pump with too much capacity draws water toward the well too fast and drags sand out of the aquifer with it.
• The screen or casing is worn or corroded. Once the screen fails, silt and sand come straight in.
• Geology. Wells drilled through sandstone, limestone or other sandy layers can carry fine sand, and shallow wells are more prone to it.

Sand showing up right after a new pump goes in often points at the first two. Sand that creeps up over the years points at the screen or casing.

What sand does to your system

Sand is abrasive. Boshart says it can wear out a pump rapidly, along with faucets, fixtures, appliances and any treatment equipment downstream. It also clogs ordinary sediment cartridges early, which is how many people find out they have a problem: the filter that used to last months is brown in a couple of weeks.

If your pump is short-cycling or pressure is dropping as well, check signs of a bad well pump.

Choosing a sediment in well water filter

Filter coarse to fine. One cartridge trying to catch everything clogs fast.

Stage 1: spin-down (spin-out) separator

A spin-down filter goes after the pressure tank. It uses centrifugal force to throw heavy sand out of the water, and a stainless mesh screen catches what's left. Boshart says a 100-mesh screen is typically enough for sand, with 250 to 500 mesh for fine silt. You clear it by opening a purge valve at the bottom, and an automatic flush valve is an option.

The nice thing about a spin-down: the screen is washable, so you aren't buying cartridges every month while the well problem gets sorted.

Stage 2: cartridge finishing filter

Downstream, a whole-house cartridge filter catches finer particles. Boshart lists finishing cartridges rated at 10, 5 or 1 micron. Pleated cartridges can be rinsed and reused a few times; string-wound and spun polypropylene ones get thrown out. Boshart puts normal cartridge life at 4 to 6 months, so if yours is clogging much faster, the well is still making sediment.

Swap a cartridge when the water pressure in the house drops noticeably, or on the calendar, whichever comes first. Keep a spare and a housing wrench next to the filter. The O-ring is the part that fails, so buy one with each cartridge and use a dab of silicone grease.

For bigger whole-house options, including backwashing filters, see whole house water filters for well water.

Fixing the cause

Filters protect the house. These fix the well:

• Raise the pump. Boshart says a well contractor can raise the pump 10 to 20 feet to stop it drawing sand.
• Slow the pump down. A flow control device, such as Boshart's FLO-TROL Model CD900, cuts pumping capacity and water velocity into the pump, which often stops sand being drawn in.
• Inspect the screen and casing. A licensed driller or pump contractor can camera-inspect the screen, and may recommend a new liner or casing, or a screen over the pump.
• Right-size the pump when it's time to replace it. See well pump sizing.

Boshart's advice is to call a licensed well driller or pump contractor right away when a well starts pumping sand. We agree. Every week of sand is wear on a pump that costs far more than the service call.