Is Birmingham water hard or soft?

Part of our hard water guide

What do Severn Trent's zone figures say about Birmingham, and what can they not tell you about your own tap, which a 20-in-1 test strip can check?

By Andrew Tomlinson, WaterKit · Last reviewed 29 October 2026

How hard is the water in each Birmingham zone?

Soft or moderately soft in every Severn Trent zone we found. Its water quality checker gives each supply zone a hardness in degrees Clark and a label, for the year to 31 August 2026. We tried 111 postcodes across B1 to B38 and four in B45, and found 23 zones, 3 labelled Soft and 20 Moderately Soft. That is a sample, not Severn Trent's full list.

The mg/l column is our own conversion from degrees Clark, at about 14.3 mg/l of calcium carbonate per degree Clark. The Drinking Water Inspectorate calls up to 100 mg/l soft, so every zone below is soft on its scale. By our reading, Severn Trent's labels change at about 3.5 degrees Clark, or 50 mg/l.

These are 5 of the 23 zones, chosen to show the range. Our hardest tap water guide places Birmingham well below the hard-water towns.

Why is Birmingham water soft?

Because most of it comes from Wales. Severn Trent's checker describes the supply to 21 of the 23 zones we found as water from the Welsh mountains, treated at works in Birmingham. The DWI says hardness varies with local geology, and we have not matched this source to its rocks.

The two highest zones are different. Hagley North and Hagley South, at 5.92 degrees Clark, are the only zones in our sample whose description adds ground water. That the groundwater zones are the hardest we found is our observation, not Severn Trent's.

Why might your tap not match the Birmingham zone figure?

Severn Trent says its table shows typical values for your area, and that individual results may vary slightly because of natural changes in the raw water and changes within the domestic plumbing system.

“I would treat the zone figure as a starting point rather than the final word, because it is an average and your own plumbing and exact zone edge can make a difference. A quick test at your own kitchen tap is an easy way to see how it compares.”

Zone edges matter too. One postcode can fall in more than one zone, so the checker may ask for your address. B45 9QQ, in Cofton in the Bromsgrove district, returned Hazy Hill at 12.11 degrees Clark, about 173 mg/l by our conversion, labelled Moderately Hard and described as ground water treated at works in Worcestershire. All five Sutton Coldfield postcodes we tried (B72 to B76) returned no Severn Trent result in our lookups, as did four elsewhere in the city. Severn Trent's checker says a postcode may be outside its region or have its water supplied by another company, such as South Staffs Water. Cambridge Water, which shares one licence with South Staffs Water, lists Sutton Coldfield in South Staffs Water's area. The DWI also says its map does not show local variation, and advises asking your water company for an accurate measurement.

How can I check my own tap?

Look up your postcode in Severn Trent's checker, then test your own tap. Our hardness by postcode guide covers other companies.

The strip has a hardness pad. Fill a clean glass or cup, dip one strip, wait 30 to 60 seconds and match the pad to the chart, or enter the colours in our free results checker (scan the QR code on the chart, no app or account needed). Our hardness testing guide has the method.

The pad has colour steps at 0, 25, 50, 100, 250 and 425 mg/l. The next lines are our own reading of the chart, not Severn Trent's. The pad's unit basis is unconfirmed, so we read it as calcium carbonate. On that reading, a zone at about 35 would sit between the 25 and 50 steps, zones from 50 to 58 around the 50 step, and 85 between 50 and 100, nearer 100. The pad shows steps, so it cannot tell 50 from 58, and a strip result is not a legal sample.

The Birmingham figure is an average, and Severn Trent says individual results vary with the raw water and domestic plumbing, so your tap may differ from its zone. On the strip, the hardness pad is the one to watch, and a reading at 250 mg/l or above would indicate harder water than any zone in our table (our filter or softener guide covers the choices). Best pack: 20 strips, enough to read your kitchen tap on a few different days and compare it with your zone figure, £5.99 (or £10.99 with a bacteria test), with free 2nd Class delivery on every order. See the kit

Your Birmingham water hardness questions

Does Birmingham have hard water?

Not in the 23 Severn Trent zones we found, all labelled Soft or Moderately Soft. Sutton Coldfield is the exception to check, and Cofton, just outside the city, returned a Moderately Hard zone.

Is Birmingham water hard or soft?

Mostly soft. Even the two highest zones, Hagley North and South, sit under the DWI's 100 mg/l soft band by our conversion.

Sources

1. Drinking Water Inspectorate, Water hardness / hard water (calcium and magnesium; varies with local geology; bands in mg/l calcium carbonate, soft up to 100; map does not show local variation; scaling; soft water at 100 mg/l or less more corrosive to pipework; undated page; read 29 October 2026).
2. Severn Trent Water, Check my water quality (page shows data updated up to 30 August 2026, 23:00 UTC; typical values, individual results may vary slightly because of the raw water and domestic plumbing; zone hardness in degrees Clark, labels, zone descriptions and the no-result message are for the postcodes we entered on 25 October 2026 and named in this guide; undated page; page read 29 October 2026).
3. WaterKit's own conversion of degrees Clark to mg/l of calcium carbonate, at about 14.3 mg/l per degree (our arithmetic, not a figure from Severn Trent or the DWI).
4. South Staffs Water, water hardness page (says all of the water it supplies is hard; undated page; read 25 October 2026; not linked because we have not checked its website terms).
5. Cambridge Water, Who we are (South Staffs Water's area includes Sutton Coldfield; both businesses operate under a single water licence; undated page; read 29 October 2026).
6. WaterKit, Water Test Kit (20-in-1 strip, 30 to 60 second read, 20 strips £5.99 or £10.99 with a bacteria test, free 2nd Class delivery on every order) and results portal (hardness steps 0, 25, 50, 100, 250 and 425 mg/L; read 29 October 2026). The reading of the chart steps against Severn Trent's figures is WaterKit's own.

Contains public sector information licensed under the Open Government Licence v3.0.