Water hardness

GU5 Guildford

Harder than the UK average. Expect visible limescale on kettles and taps.

At 307 ppm, Guildford sits among the UK's hardest water areas — compare it against the softest areas.

Very Hard 307 ppm South East Thames Water

Your reading

307

parts per million

Soft

Moderate

Hard

Very hard

0100200300400+

What this means for your home

Based on 307 ppm in Guildford (very hard water).

Heavy limescale requiring frequent descaling
Blocked showerheads and reduced water flow
Substantially higher energy bills from boiler scale
Dry, itchy skin and lifeless hair
White crusty deposits on taps and surfaces
Reduced lifespan of washing machines and dishwashers

Heat loss

12%

Heavy scaling

Softener salt

£18–30

per year

Worth it?

Yes

at 307 ppm

Suggested for very hard water

Whole-house water softener

Best long-term protection for boilers and pipes.

From £600 installed

Shower head filter

A simple first step for limescale on tiles and glass.

From £25

Filter jug or under-sink

Improves taste and reduces kettle scale.

From £20

Softening

Should you soften the water in Guildford?

A verdict and running-cost estimate based on GU5's 307 ppm reading, for a typical 4-person household.

Softener recommended

Water is hard to very hard, so appliance, scale and soap savings typically pay back a softener within a few years.

Recommended size

24k

grain capacity, regenerates ~every 8.7 days

Salt running cost

£18–30

per year (~63 kg salt)

Limescale

12%

est. heater efficiency loss. Heavy scaling

Soap saving

High

Large saving: many homes cut soap, shampoo and detergent use by up to half.

Appliance impact at 307 ppm: significant: elements fur up, expect earlier failures. Sized for a 4-person home; regenerates roughly every 9 days (estimate). Figures are conservative estimates and vary with household size and usage.

Recommended

Products for Guildford

Popular choices for households dealing with very hard water.

Splendid Twin Tank Water Softener

From ~£400

Twin-tank electric softener sized for 1 to 7 bedroom homes. Removes limescale from pipes, boilers, and appliances and delivers continuous soft water, with metered regeneration to keep salt use low.

View on Amazon

Philips Shower Filter

From ~£30

Quick win for skin and hair in hard water areas. Reduces chlorine and limescale, fits standard shower hoses in minutes, no tools needed. Cartridge lasts around 6 months.

View on Amazon

BRITA Marella Water Filter Jug

From ~£20

UK's best-selling filter jug. Reduces limescale, chlorine, and metals for better-tasting tap water. Quick first step alongside a softener.

View on Amazon

Water quality details

Hardness data for GU5

Sourced from Thames Water's published water-quality reports and public records.

Hardness measurements

Parts per million (ppm CaCO₃)	307
Degrees Clark (°Clark)	21.5
Degrees French (°fH)	30.7
Degrees German (°dH)	17.2
Calcium (mg/L Ca²⁺)	123

Supplier and area

Water supplier Thames Water

Region South East

County Surrey

Hardness band Very Hard

UK average 207 ppm

Visit Thames Water page

Official source

Thames Water Utilities Ltd water-hardness report

Read the hardness categories table to see where your supply falls; most of the region is hard to very hard at over 200 mg/l CaCO3.

Nearby

Other areas near Guildford

FAQ

Common questions about GU5

What is the water hardness in GU5 Guildford?

The water in GU5 Guildford has a hardness level of 307 ppm (parts per million) calcium carbonate, classified as very hard. This is 100 ppm above the UK national average of 207 ppm.

Which water company supplies GU5?

GU5 Guildford is supplied by Thames Water. Thames Water serves the South East region.

Is the water in GU5 safe to drink?

Yes. Very Hard water at 307 ppm is safe to drink. Water hardness affects taste and can cause limescale, but it is not a health risk. In fact, hard water contains beneficial minerals like calcium and magnesium.

How can I reduce water hardness in GU5?

For very hard water at 307 ppm, a whole-house water softener is the most effective solution. You can also use a jug filter for drinking water, descaling products for appliances, and a shower filter for better skin and hair.

What does 307 ppm water hardness mean?

307 ppm means there are 307 parts per million of calcium carbonate dissolved in the water. This is equivalent to 21.5 Clark degrees, 17.2 German degrees, or 30.7 French degrees. Water above 180 ppm is generally considered hard.

What size water softener do I need in GU5?

For a typical 4-person home at 307 ppm, a 24,000 grain softener is a sensible size. It would regenerate roughly every 8.7 days. Larger households or higher daily use need a bigger unit. These figures are conservative estimates.

How much does it cost to run a water softener in GU5?

At 307 ppm, expect to use about 63 kg of salt a year, costing roughly £18–£30/year. Water is hard to very hard, so appliance, scale and soap savings typically pay back a softener within a few years.

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