SW1A Water Hardness
Based on nearest verified measurement point: London (0.4 km away)
Calcium Carbonate equivalent · Nearest municipality: London
Admin area: Westminster
What This Means for Your Home
Kettle descaling
Every 4–6 weeks
Dishwasher salt
Top up monthly
Boiler risk
High — annual descaling required
Shower filter
Strongly recommended
Tools for Your Hardness Level
Boiler Warranty Checker
See if your hardness voids your warranty
Dishwasher Salt Settings
Calibrate for 277 mg/L
Skin & Hair Checker
Check eczema and hair damage risk
Baby Formula Safety
Is it safe to make formula with your water?
Limescale Cost Estimator
Annual cost of hard water for appliances
Pool Chemical Calculator
Doses adjusted for your source water
Data note: Postcode hardness is matched to the nearest verified municipal measurement point in our dataset. Actual hardness at your specific address may vary slightly depending on local pipe infrastructure and your water supplier's supply zone. For verified postcode-level data, consult your water supplier directly. Water supply company for this area: Thames Water.