Total Hardness of Water

The dissolved calcium and magnesium in your water.

Hardness is simply the amount of dissolved calcium and magnesium your water carries. It’s not a health risk — but it’s the marker behind most everyday water complaints: scale in the kettle, spots on glasses, stiff laundry, dry skin and hair, and appliances that wear out early.

What it is

Water picks up calcium and magnesium as it moves through limestone and chalk deposits, and the total is expressed as hardness (GH). Soft water lathers easily; hard water resists soap and leaves minerals behind wherever it evaporates.

How it varies

Hardness is almost entirely about local geology — some regions have naturally soft water, others very hard. Well water in limestone country typically runs hardest. It changes little day to day, so one good measurement tells you a lot.

What a result can tell you

There’s no federal limit, but below roughly 150 mg/L is generally considered comfortable for homes. Higher readings explain scale buildup and appliance wear, and tell you whether a water softener would earn its keep. If you already have a softener, testing confirms whether it’s actually working.

What it can’t tell you

Hardness says nothing about safety — hard water can be perfectly healthy to drink, and some evidence suggests dietary minerals in water are mildly beneficial. Treat this marker as a home-maintenance and comfort question, not a health one.