Why your well water leaves white crust and scale, and how to fix it

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Step 1: Check for the other signs of hard water

White crust rarely shows up alone. The Wisconsin DNR and Penn State Extension list these signs:

• White or grayish-white film in sinks, tubs, and on dishes
• Scale inside the tea kettle and around faucets
• Soap and shampoo that won't lather well
• Soap scum in the tub and curds in the washing machine
• White flakes in the water

If you see several of these, hardness is the likely cause.

Hard water comes from the rock your well draws from

Calcium and magnesium dissolve from limestone and other rock as groundwater moves through it. Hard water isn't a health risk, and there's no drinking water limit for it. The trouble is the scale. Wisconsin says it lowers the efficiency of water heaters and shortens the life of appliances that use water.

A white crust can also come from very high pH. The EPA lists "deposits" and a slippery feel as effects of pH above 8.5.

Step 2: Find out how hard your water is

Test strips give a rough number. A lab test gives an exact one, and it's worth adding iron, manganese, and pH, since those change which softener fits.

Penn State uses this scale:

Penn State, Virginia Cooperative Extension, and Minnesota all point to about 120 mg/L, or 7 grains per gallon, as the level where hardness starts causing scale and soap problems.

A softener fixes it, with tradeoffs

The standard fix is an ion exchange water softener. It swaps the calcium and magnesium for sodium (or potassium, if you use potassium chloride). Virginia Cooperative Extension warns that extra potassium can be a health risk for people with kidney disease and conditions such as heart disease, high blood pressure, or diabetes, so ask a doctor first if that's you. Penn State says hardware usually costs $500 to $1,500, not counting installation and upkeep.

Things to know before you buy:

• It adds sodium. Penn State says softening adds about 7.5 mg of sodium per quart for each grain of hardness removed. Virginia Cooperative Extension says people on low-sodium diets should talk to a doctor first.
• You can skip the drinking water. Virginia Cooperative Extension suggests leaving the cold kitchen tap unsoftened, or softening only the hot water.
• It can make water more corrosive. Minnesota says softened water can corrode pipes and raise lead and copper levels.
• It needs salt and upkeep. You add salt to the brine tank, and the salty rinse water goes down the drain.

When to call a pro

Get a lab test and talk to a water treatment professional if your water is very hard and also has iron, manganese, or low pH. A softener has to be sized for all of it, and Virginia Cooperative Extension recommends a certified lab test before buying any treatment.

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