Water quality
Is hard water bad for plumbing?
Updated · Editorial team; not yet technically reviewed
Short answer
Hard water isn't a health problem, but it is hard on plumbing. The calcium and magnesium in it form scale when water is heated or evaporates, which shortens water heater life, clogs tankless heat exchangers, aerators and shower valves, and narrows older metal pipes. The harder the water, the more maintenance or softening pays off.
Hardness levels
| Class | Milligrams per liter (ppm) | Grains per gallon |
|---|---|---|
| Soft | 0–60 | 0–3.5 |
| Moderately hard | 61–120 | 3.6–7 |
| Hard | 121–180 | 7.1–10.5 |
| Very hard | Over 180 | Over 10.5 |
Your water utility's annual water quality report usually lists hardness. Our city guides show it where the utility publishes a figure; see locations.
Where hard water does damage
- Tank water heaters: scale settles on the bottom, causing popping and rumbling, longer burner run times and early failure. Electric elements can burn out under it.
- Tankless heaters: scale coats the heat exchanger. Most manufacturers call for periodic descaling, more often in hard-water areas. See tankless water heaters.
- Fixtures: clogged aerators and showerheads, stiff cartridges and shower valves, and running toilets from scaled fill valves.
- Appliances: dishwashers and washing machines lose efficiency as scale builds on heating elements and valves.
- Older galvanized pipe: scale and corrosion together narrow the bore and reduce pressure.
What to do about it
| Option | What it does | Best for |
|---|---|---|
| Regular flushing and descaling | Removes scale from heaters before it hardens | Moderately hard water; anyone with a tankless unit |
| Water softener | Ion exchange swaps hardness minerals for sodium or potassium | Hard and very hard water, whole house |
| Scale-reduction (template-assisted crystallization) systems | Changes how minerals form so less scale sticks; doesn't remove them | Where salt discharge is restricted or not wanted |
| Point-of-use filters | Improves taste; most don't soften | Drinking water only |
Common questions
Does a water softener make water unsafe to drink?
Softened water contains added sodium. For most people the amount is small, but people on low-sodium diets often keep an unsoftened tap for drinking or use potassium chloride.
Can hard water cause low water pressure?
In older galvanized or copper pipes, scale can narrow the pipe over many years. More often it clogs aerators and showerheads, which is an easy fix.
General information; codes vary by location. See our editorial standards.