Where does this data come from?

Our water hardness figures are sourced from South West Water's published water quality data, as compiled by WaterHard.uk. South West Water tests and publishes this data regularly as part of their legal obligations under the Water Supply (Water Quality) Regulations. You can also check your water quality directly on the South West Water website.

Why is East Devon water harder than the rest of the South West?

Most of Devon and Cornwall gets its water from moorland rivers and reservoirs, which produce naturally soft water. East Devon is different — the water here comes from 14 boreholes drilled deep into the Otter Valley. As water filters through the local Triassic sandstone, it picks up dissolved calcium and magnesium minerals, making it noticeably harder than the rest of the South West Water supply area.

What ppm counts as hard water?

In the UK, water hardness is measured in parts per million (ppm) of calcium carbonate. Under 60 ppm is soft, 60–120 ppm is slightly hard, 120–180 ppm is moderately hard, and above 180 ppm is hard. East Devon falls in the slightly hard range (63–83 ppm), which is still below the UK national average of around 207 ppm.

Do I need a water softener in Exmouth?

With water hardness around 82 ppm, most Exmouth homes won't need a water softener. You may notice minor limescale on taps and in kettles, but it's manageable with occasional descaling. A water softener (£1,200–£2,000 installed) is generally better suited to areas with hardness above 200 ppm. A plumber can advise based on your specific situation.

How does slightly hard water affect my boiler?

At the hardness levels found in East Devon (63–83 ppm), the impact on your boiler is minor compared to truly hard water areas. You may see some limescale buildup over time, but regular annual servicing is enough to keep things in check. The bigger risk to boilers in this area is age and general wear rather than scale.

Check Your Water Hardness — Exmouth & East Devon

East Devon has the hardest water in the South West Water region — but how does it compare to the rest of the UK? Enter your postcode to find out.

What's your postcode?

We'll look up the water hardness for your area. We currently cover Devon postcodes (EX1–EX24).

Did you know? Most of Devon and Cornwall gets naturally soft water from moorland rivers and reservoirs. East Devon is the exception — water here comes from 14 boreholes in the Otter Valley, where it picks up minerals from the local sandstone, making it the hardest water in the South West Water region.

How East Devon Compares

ppm in Exmouth

ppm South West Water average

207

ppm UK national average

UK Water Hardness Scale

Soft

0–60 ppm

Slightly Hard

60–120 ppm

East Devon

Moderately Hard

120–180 ppm

Hard

180+ ppm

East Devon has the hardest water in the South West Water region, but it's still classified as slightly hard — well below the UK average.

Water Hardness FAQs

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