Cloudy, milky or sandy well water: causes and what to do

Cloudy water from a well has two very different explanations. One is air, which looks alarming and means little. The other is sediment: sand, silt or clay coming in with the water, which tells you something has changed in the well. A glass of water is enough to tell them apart.

The glass test

Fill a clear glass with cold water and set it on the counter.

What you see	Likely cause
Milky water that clears on its own within a few seconds	Tiny air bubbles
Grit you can see or feel that sinks to the bottom	Sand
Muddy or hazy water with fine particles that settle slowly	Silt, clay or other fine sediment
Water comes out clear, then turns rusty or leaves orange or black specks	Iron or manganese

Sources: USGS, Massachusetts Executive Office of Energy and Environmental Affairs, University of Georgia Extension.

Air. The US Geological Survey explains that water in household pipes is under pressure, which keeps air dissolved in it. In the glass, that air comes out as tiny bubbles, which rise and leave the water clear¹.

Sediment. Turbidity is the technical word for cloudiness caused by suspended material such as clay, silt and fine organic matter⁴. If it settles, it’s solid, and it came from the well or the plumbing.

Rusty color. If the water starts clear and changes color as it sits, see our guide to iron and manganese in well water.

If it’s air

Bubbles that clear in seconds are usually nothing more than dissolved air¹.

There is one case worth watching. Massachusetts’ guidance for well owners says air bubbles from faucets that don’t have an aerator can be a sign that the pump can’t fill the pressure tank before the water level in the well drops to the pump’s intake, so it sucks in air². That is a low-water problem, most likely during a drought. The same guidance says the pump may then run for longer than normal².

If it’s sand or sediment

Sediment that wasn’t there before means something has changed. Extension and state sources list these causes:

• A falling water table. When the water level drops, water enters the well through a smaller area and at a higher speed, which can pull more silt and sand in with it². The University of Georgia also mentions water cascading into the well when the water table drops⁴.
• The well screen. In wells drilled into sand and gravel, a screen holds the formation back. Sediment gets through when the screen is the wrong size, badly placed or corroded³⁴. Penn State notes that corrosion can enlarge screen openings³.
• Pumping too hard. Penn State lists overpumping a well beyond its design capacity as a cause of sediment problems³.
• Fractured rock. A well drilled through fractured rock can have turbidity problems, and the grit can damage the pump⁴.
• A new well. Solids left over from drilling can make a new well cloudy at first. They are usually removed by a period of continuous pumping called well development⁴. Penn State calls proper well development the most important way to prevent this kind of plugging³.
• A lowered pump. Lowering the pump to reach water during a drought can bring in more sediment than the old setting did².

Why it matters

Your pump. Penn State Extension says abrasion from pumping sand is the leading cause of pump failure³. It also lists more sand or sediment in the water as one of the signs that a well is losing performance³.

Your plumbing. Sediment can clog fixtures and filters and cut the flow at your taps².

Your health. The University of Georgia says the main problem with turbidity is appearance, but that suspended matter can carry pathogens with it, and harmful contaminants may be attached to soil and clay particles⁴. Its rule of thumb: if turbidity is above 5 turbidity units, be alert to possible bacterial contamination⁴.

What to do, in order

1. Do the glass test with cold water, and note when it started and whether anything changed: a dry spell, heavy use, work on the well.
2. Send a sample to a certified lab⁶. Ask for coliform bacteria, and add iron and manganese if the particles are orange or black. Our well water testing guide explains how to find a lab.
3. Call a licensed well contractor if you see sand, or if the cloudiness doesn’t go away. Penn State’s advice when a well loses performance is to have a professional water well contractor inspect it, and it mentions a downhole camera inspection as a way to see what is happening inside³.
4. Protect the house with a filter while the cause is being fixed (next section).

Fixes at the well depend on what the contractor finds. Penn State mentions replacing a damaged screen, fitting a smaller-diameter liner inside it or using flow-control devices to reduce sand pumping, and warns that fixing recurring sand pumping is sometimes cost-prohibitive³. It also says that delaying rehabilitation can significantly increase costs³.

Sediment filters

A sediment filter is a physical strainer. It doesn’t disinfect the water, and it doesn’t stop sand from passing through the pump first.

• Cartridge filters are rated in microns: the smaller the number, the finer the particles they catch. NDSU Extension suggests 10 to 15 microns for drilled wells and the finest available, 2 microns, for dug or bored wells, which often contain fine clay⁵. Finer filters need more pressure to push water through⁵.
• For heavy sediment, the University of Georgia suggests a new well screen together with a cartridge sediment filter, or an automatic sand filter that backwashes itself⁴.
• Change cartridges when they clog. Georgia warns that bacteria can grow in spent filter media⁴, and NDSU notes that a loss of pressure at the tap can mean a clogged filter⁵.
• If a filter that used to work stops working, the sediment may have become finer. Massachusetts suggests a cartridge with a smaller micron rating, a larger filter, or extra filters installed in parallel².

Thinking about a water softener as well? Sort out the sediment first, then use our water softener size calculator to see what your hardness test means.