how hard is my water?
Water Hardness Checker
Instantly check your area by postcode
Curious about the water hardness in your area? Our free tool lets you check instantly. Simply enter your postcode to see whether your water supply is classed as hard, medium or soft.
UK Water Hardness Checker – Check Your Area by Postcode
Enter your postcode to see whether your water is soft or hard, get the figure in mg/l and °Clark, and find out what it means for limescale in your home.
Got a figure from your water company? Convert it
UK water companies publish hardness in mg/l, mmol/l, or degrees Clark, French or German — Severn Trent, for example, gives three degree scales and no mg/l figure at all. Degrees Clark is also written °e or English degrees, which is what most appliance manuals call it. Enter whichever number you have and we'll convert it to the rest.
Classification: —
Suggested Saniflo descaling: —
What is water hardness?
Water hardness is the level of dissolved minerals — mainly calcium carbonate — in your supply. The more there is, the more limescale forms in kettles, shower heads, boilers and anything else that heats water. It is also a common and avoidable cause of Saniflo macerator failure, where scale coats the impeller, narrows the discharge pipe and forces the motor to work harder until it gives up.
Quick tip: hardness is set by your supply zone, not your town. Two postcodes a few miles apart can be fed from completely different sources, which is why we tell you plainly whether a figure is measured or estimated.
UK water hardness scale
These are the bands used by UK water companies, so our classification should match what your supplier tells you. Regional figures shown by the checker are indicative ranges based on supply source and geology, not measurements — only results labelled verified come from published zone data.
| mg/l (ppm) | °Clark | Classification | Saniflo care |
|---|---|---|---|
| 0–50 | 0–3.5 | Soft | Annual service |
| 51–100 | 3.6–7.0 | Moderately soft | Every 9–12 months |
| 101–150 | 7.1–10.5 | Slightly hard | Every 6–9 months |
| 151–200 | 10.6–14.0 | Moderately hard | Every 4–6 months |
| 201–300 | 14.1–21.0 | Hard | Every 3–4 months |
| Over 300 | Over 21.0 | Very hard | Every 2–3 months |
Hard and soft water across the UK
Broadly, the hardest water is in London, Essex, Kent, Hertfordshire, Bedfordshire, Cambridgeshire and East Anglia, on chalk and limestone. The M4 corridor — Bristol, Bath, Swindon — plus Berkshire, Surrey, Sussex, Lincolnshire and the East Riding are hard. Scotland, most of Wales, the North West, the North East, Devon and Cornwall are soft.
But the regional picture misses a lot. Checking published supply zone data postcode by postcode turned up plenty that no hardness map shows:
- Telford, 318 mg/l — very hard, in a part of the country usually coloured soft.
- Malvern, 245 mg/l — harder than Worcester twelve miles away, despite the famous springs.
- Sheffield, 20 mg/l — among the softest supplies in England.
- Pontefract is twice Wakefield — 281 against 143, ten miles apart on the same water company.
- Bromsgrove is three times Birmingham — 175 against 53, same postcode letter, same company, entirely different source.
Birmingham is the one that surprises people most. Despite sitting on sandstone, most of the city is fed from the Elan Valley reservoirs in mid-Wales via the Victorian aqueduct and comes out genuinely soft, while parts of the wider West Midlands draw on local boreholes and are far harder. In this region the postcode really does matter.
Saniflo maintenance in hard water areas
Limescale clogs the macerator blades and impeller, narrows pipes and valves, and forces the motor to work harder. In hard water areas a unit can fail within two to three years without a descaling routine — and a descaler costs a fraction of a replacement.
- Descale to schedule: match the interval to your actual hardness, not a regional guess
- Use approved products: household descalers can damage internal components
- Professional service: an annual check prevents major issues
- Early intervention: address noise or slow drainage immediately
Frequently asked questions
Why might your result differ from my water company's?
Your water company measures your specific supply zone and publishes updated results periodically, so that is always the authoritative figure. Where we hold verified zone data we show it and name the zone. Where we don't, we give you the regional picture and tell you it's an estimate. If the two ever disagree, believe your supplier — and please tell us, so we can correct it.
How do I convert between hardness units?
To get mg/l (ppm) of calcium carbonate: multiply degrees Clark by 14.254, French degrees by 10, German degrees (°dH) by 17.848, or mmol/l by 100.087. So 3.70 °Clark is about 53 mg/l, or 0.53 mmol/l. The converter above does all of them.
What setting should I use on my dishwasher or washing machine?
Appliance manuals usually ask for German degrees (°dH) or mmol/l, and some older ones ask for °e, which is another name for degrees Clark. All of those are shown with your result above, so you can read the right number straight off. If your manual gives a scale of 1 to 10 rather than a unit, check what range it maps to — they vary by manufacturer.
How often should I descale my Saniflo?
It depends on your hardness. Under 50 mg/l an annual service is generally enough. Between 200 and 300 mg/l, every three to four months. Above 300 mg/l, every two to three months.
Is hard water bad for my Saniflo macerator?
Hard water causes limescale to build up inside the unit, reducing efficiency and eventually causing blockages and pump failure if it isn't regularly descaled with approved products.
What are the signs my Saniflo needs descaling?
Noisy running, slow drainage, frequent stops and starts, gurgling sounds, and visible limescale around the unit.
Can I use any descaler on my Saniflo?
Use Saniflo Descaler or Cleanser and follow the manufacturer’s instructions. Household descalers and unapproved chemicals such as bleach or vinegar can damage internal components, and using them may affect your warranty cover.
Will a water softener protect my Saniflo?
A whole-house softener significantly reduces scaling, but Saniflo units still need regular approved descaling as part of routine maintenance.
Pumpmaster UK: Approved Saniflo repair specialists since 1989. Certified engineers covering England & Wales.
Give us a call: 0800 292 2542