Soft WaterSouth West WaterSouth West

Plymouth Water Hardness Report

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

Average City Tap Water RatingUpdated 18 May 2025
34PPM (mg/L CaCO3)
Clark Degrees
2.4° Clark
French Scale
3.4°fH
German Scale
1.9°dH

Plymouth tap water is amongst the purest and softest in the UK, measuring an average of just 34 PPM. South West Water sources Plymouth's supply from Dartmoor National Park (Burrator Reservoir) and the River Tamar. Flowing across impermeable Dartmoor granite and peat moorlands, the water collects virtually no calcium or magnesium. Plymouth households enjoy scale-free kettles, sparkling shower glass, and luxurious soap lather, with zero need for domestic water softeners.

83% softer than the UK national baseline (200 PPM)

Neighbourhood Hydro-Variance

Water hardness across Plymouth varies by up to 23 PPM between different treatment zones and boreholes.

Softest District25 PPM
Peverell & Hartley
Hardest District48 PPM
The Hoe & Barbican
Supplied by South West Water under Drinking Water Inspectorate (DWI) regulatory standards.
Local Installer Quote Network

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Which?-Style Practical Household Advice

Living with Plymouth Tap Water: Essential Household Guide

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

Kettles & Hot Drinks

Virtually never required. A light rinse every 4–6 months clears natural dust and loose sediment.

💡 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 0 or 1 (Minimum). Multi-benefit all-in-one tablets supply all conditioning needed.

⚙️ Recommended Dial Setting: Level 1 / Off (refer to machine manual).
Boiler Efficiency & BS 7593

Zero mineral scale drag on combi boiler heat exchangers. Maintain system corrosion inhibitor under BS 7593.

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

Soaps and shampoos lather effortlessly with tiny amounts. Kind to sensitive skin and eczema sufferers.

🚿 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 Plymouth Tap Water

Is Plymouth water soft or hard?
Plymouth water is very soft, averaging 34 PPM. It is gathered from granite moorland catchments on Dartmoor.
Do I need dishwasher salt in Plymouth?
No, dishwasher salt is largely optional in Plymouth. Set the hardness regulator to setting 1, and standard detergent tablets will handle the rest.
Will limescale build up in my boiler in Plymouth?
No, limescale buildup is virtually non-existent. However, soft water can be slightly acidic, making corrosion inhibitor dosing under BS 7593 important.
WaterHardness.uk Technical & Water Quality Research Team
Data sourced from South West Water compliance reports and Drinking Water Inspectorate (DWI) public records.