UK Water Quality Report • 2026 Data

Water Hardness in SL4

Water supply analysis across 7 postcode sectors in SL4 (Thames Water).

Outcode Avg Hardness276.4 PPMHard Water
Regional Quality Overview

Water Supply Analysis: Outcode SL4

For residents and businesses in outcode SL4, understanding local water chemistry is essential for appliance longevity and limescale prevention. Our environmental data shows that SL4 averages 276.4 PPM in mineral content, falling into the Hard Water classification.

Water chemistry can fluctuate across supply zones in SL4. The lowest mineral concentration is recorded in sector SL4 4 at 270 PPM, whereas sector SL4 2 experiences higher mineral levels reaching 290 PPM.

Due to the hard water (276.4 PPM) in SL4, limescale build-up can occur on heating elements, shower heads, and boilers. Setting your dishwasher water softener to the correct level (e.g. Bosch setting H04) is strongly recommended to prevent cloudy glassware and internal scale accumulation. Review the individual postcode sectors below to get precise dishwasher salt settings and limescale recommendations.

Softest Sector in SL4

Lowest mineral concentration

Softest
Sector SL4 4294 Postcodes • Hard
270 PPM18.9 °Clark

Hardest Sector in SL4

Highest mineral concentration

Highest Hardness
Sector SL4 2216 Postcodes • Hard
290 PPM20.3 °Clark

All Postcode Sectors in SL4

Select a postcode sector below to view exact water softener salt settings, limescale protection guides, and appliance recommendations.