Much of southern and eastern England sits on chalk and limestone. The water is hard, and every litre that goes through your appliances leaves a little calcium carbonate behind.
It builds slowly enough that nobody notices, and then a heating element fails at four years old on a machine that should have lasted ten.
Here's what it actually does, and what's worth doing about it.
Where the damage happens
The heating element
This is the expensive one. Both your washing machine and your dishwasher heat water with an element, and limescale deposits on hot metal first.
A scaled element has to work harder and run longer to reach the same temperature. That costs you money every cycle, and eventually the element overheats under its own insulating layer and fails. On most machines, replacing one costs enough that people buy a new machine instead.
The spray arms and jets
In a dishwasher, scale narrows the holes in the spray arms. The water still goes in, but it comes out as a dribble rather than a jet, so plates come out with food still on them. People assume the dishwasher is failing when it's actually blocked.
Our guide to a dishwasher that isn't cleaning properly covers the full diagnosis.
The drum and the smell
In a washing machine, scale gives detergent residue and biofilm somewhere to cling. That's a large part of why machines in hard water areas start to smell — covered in our guide to why your washing machine smells.
The bit that catches people out
Limescale damage is generally excluded from appliance warranties.
Manufacturers treat it as a maintenance issue rather than a defect, in the same way they treat blocked filters. A failed element at three years old, opened up and found packed with scale, is very often a declined claim.
This is not manufacturers being difficult — scale is preventable, and they know it. But it does mean the maintenance is genuinely worth doing. Our warranties guide goes through what's covered and what isn't.
How to tell if you have it
You don't need a test kit. Look for:
- White or cloudy film on glasses out of the dishwasher — the classic sign
- Chalky residue round the kettle element or taps
- Cycles taking longer than they used to
- Detergent not lathering, or needing more of it for the same result
- Crusty white deposits in the washing machine drawer
Your water company publishes hardness by postcode on their website, usually free and instantly.
What actually works
Use dishwasher salt — yes, even with all-in-one tablets
This is the single most useful thing on the list, and the most often skipped.
Nearly every dishwasher has a built-in softener with a salt reservoir. All-in-one tablets contain a small amount of softening agent, and the packaging implies you don't need salt. In a hard water area that is not enough.
Fill the salt reservoir, set the machine's hardness level to match your area (it's in the settings menu, and almost nobody changes it from the factory default), and top it up when the light comes on.
Salt is a few pounds a box. An element is not.
Run a maintenance wash
Once a month, run both machines empty on the hottest cycle with a proper descaler or citric acid. Not a quick wash — it needs the heat and the time.
On a washing machine, leave the door and drawer ajar between washes so it dries out.
Dose detergent for your water, not the box
Hard water needs more detergent to work; soft water needs considerably less. Most detergent packaging gives a hard-water dose as standard, which is why people in soft areas get residue. Check the box — most give both.
Whole-house softener
A plumbed-in softener treats every appliance, the boiler and the shower. It's a real cost and needs a plumber and an under-sink space, but in a very hard area it pays back over a decade across everything, not just the appliances.
Worth pricing if you're already having plumbing work done. Not worth it for one dishwasher.
Machines with a decent built-in softener
Every dishwasher we sell has a salt reservoir. These are the ones where the softener is a genuine feature rather than a box-tick:
- CDA CDI6121 60cm Integrated — £389
- Montpellier MDWBI6064 60cm Integrated, 14 place — £429
- Rangemaster T60 Integrated, 12 place — £490
- Samsung Series 7 Integrated 60cm — £499
- Smeg DI362DQ 60cm Fully Integrated, 13 place — £529
On a budget, the White Knight AT45FSDW 45cm at £238.99 and the Candy CI3E53E0W-80 full-size integrated at £319 both take salt — just remember to use it.
Frequently asked questions
Do I need dishwasher salt if I use all-in-one tablets?
In a hard water area, yes. The softening agent in a tablet is a supplement to the salt reservoir, not a replacement for it. In a genuinely soft area you can usually get away without.
How do I find out how hard my water is?
Your water supplier publishes it by postcode on their website. It's the most reliable source — more so than a general map, because supply areas don't follow county lines.
Does limescale affect a tumble dryer?
Not really. A condenser or heat pump dryer doesn't take a mains water feed, so there's nothing to deposit. Keep the filters and condenser clean instead.
Will a descaler fix a machine that's already scaled up?
It will help, and a monthly maintenance wash will stop it getting worse. It won't reverse years of buildup on an element that's already failing.
Is a water softener worth it just for the appliances?
On its own, probably not. Across a whole house — boiler, shower, kettle, taps and appliances together — in a very hard area, the case is much stronger.
Why do my glasses come out cloudy?
Usually limescale, sometimes etching from over-dosing detergent in soft water. If the film wipes off with vinegar it's scale. If it doesn't, it's etching and it's permanent — and you should use less detergent.
Not sure whether your area is hard? Tell us your postcode and we'll tell you what to look for before you buy.
