Hard WaterPortsmouth WaterSouth East

Portsmouth Water Hardness Report

Official mineral water quality analysis, local catchment breakdown, appliance salt calibration, and postcode outcode directory for Portsmouth.

Average City Tap Water RatingUpdated 23 June 2026
290PPM (mg/L CaCO3)
Clark Degrees
20.3° Clark
French Scale
29.0°fH
German Scale
16.2°dH

Portsmouth tap water is naturally very hard, with an average hardness rating of 290 PPM. Portsmouth Water abstracts water from the world-famous natural chalk springs at Havant and Bedhampton, together with River Itchen borehole transfers. The water has spent months slowly filtering through deep South Downs chalk, absorbing massive quantities of calcium bicarbonate. While beautifully clear and refreshing to drink, it leads to rapid kettle scaling, cloudy glassware, and stiff laundry unless treated.

45% harder than the UK national baseline (200 PPM)

Neighbourhood Hydro-Variance

Water hardness across Portsmouth varies by up to 50 PPM between different treatment zones and boreholes.

Softest District265 PPM
Southsea & Old Portsmouth
Hardest District315 PPM
Cosham & Drayton
Supplied by Portsmouth Water under Drinking Water Inspectorate (DWI) regulatory standards.
Local Installer Quote Network

Living in a Hard Water Zone (PO averages 290 PPM)? Compare Approved Local Installers

Get up to 3 free, no-obligation quotes from WRAS-approved water softener installers and heating engineers serving Portsmouth.

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Which?-Style Practical Household Advice

Living with Portsmouth Tap Water: Essential Household Guide

Practical calibrations for kitchen appliances, heating systems, and personal care tailored specifically to Portsmouth's water profile.

Kettles & Hot Drinks

Monthly descaling required. Boil one tablespoon of citric acid to dissolve crust before it flakes into morning cuppas.

💡 Pro Tip: Buy food-grade citric acid powder (£5/kg) instead of chemical descaling tablets. One boiled tablespoon cleans the base in 5 minutes with zero lingering odor.
Dishwasher Salt Calibration

Level 4 or 5 (High). Essential to maintain ion-exchange resin bed and prevent cloudy glass etching.

⚙️ Recommended Dial Setting: Level 4–5 (refer to machine manual).
Boiler Efficiency & BS 7593

High scale hazard. Up to 10%–14% fuel efficiency loss without scale protection. In-line scale reducer and BS 7593 inhibitor essential.

🛡️ Compliance: British Standard BS 7593 requires regular chemical inhibitor dosing and annual testing to prevent heat exchanger scale drag.
Bathing, Hair & Sensitive Skin

Hard minerals bind to fatty acids, forming soap curd that strips natural moisture and irritates dry or eczema-prone skin.

🚿 Shower Screens: Use a rubber squeegee after each shower to prevent dissolved calcium from baking into the glass under hot steam.
Common Questions

Frequently Asked Questions about Portsmouth Tap Water

Where does Portsmouth water come from?
Most of Portsmouth's drinking water comes from natural springs at Havant and Bedhampton, emerging from underground chalk aquifers in the South Downs.
What dishwasher setting is needed in Portsmouth?
Set your dishwasher water softener to Level 5. Refill the salt container whenever the warning indicator illuminates to avoid chalk residue.
How do I remove limescale from my Portsmouth shower?
Use warm white vinegar or a citric acid spray. Avoid harsh abrasive cleaners that scratch chrome and glass surfaces.
WaterHardness.uk Technical & Water Quality Research Team
Data sourced from Portsmouth Water compliance reports and Drinking Water Inspectorate (DWI) public records.