Hard Water, Boilers and Leaks in Portsmouth

How hard is Portsmouth's tap water?

It is hard to very hard: Portsmouth Water's 2026 table puts its 15 supply zones between 263 and 310 mg/l as calcium carbonate, about 18 to 22 °Clark. The Farlington zones that serve Portsmouth itself, Southsea included, run 277 to 282 mg/l. On the Drinking Water Inspectorate's scale, anything from 200 to 300 counts as hard and anything above 300 as very hard.

The hardness comes from the ground. Rain soaks into the chalk of the South Downs and picks up calcium on the way, and most of the supply is pumped back out of that same chalk. Only three zones average over 300 or close to it: Worlds End (310), Littleheath (302) and Lovedean (296, near the very-hard line).

Zone boundaries do not follow town names, so the reliable figure for your street comes from Portsmouth Water's Zone Lookup. The hard water page goes through every zone, and the limescale page covers what that hardness leaves behind in kettles, taps and showers.

Do Portsmouth homes need a water softener?

No law requires one; the DWI calls a softener "a matter of personal choice", though on water this hard it will cut scale in appliances and on bathroom fittings. What the law does cover is fitting one. A softener that regenerates with water is on the notification list in regulation 5 of the Water Fittings Regulations, so Portsmouth Water must be told before the work starts; consent is deemed if it has not replied within ten working days.

Official advice also asks you to keep one unsoftened tap in the kitchen for drinking and cooking, because ion exchange swaps hardness for sodium. The drinking water tap page sets out who says so and why it is advice rather than law. For the choice itself, the water softeners page explains how they work, softener sizing runs the sums on local hardness, and scale reducers covers the salt-free route.

What does hard water do to a combi boiler?

It coats the hot-water heat exchanger with scale, and Vaillant's own fault table names "scale in the secondary heat exchanger" among its causes, to be descaled or the part replaced. That is why Approved Document L, para 8.8, says that in hard water areas the feed to water heaters and the hot-water circuit of combination boilers should be treated to reduce limescale. Its definition of a hard water area is over 200 ppm, and every Portsmouth Water zone clears that line.

Makers set their own thresholds and do not agree. Worcester Bosch's Greenstar 4000 manual says that where temporary hardness exceeds 200 ppm "consideration may need to be given to the fitting of a scale prevention device". Vaillant says softening above 15 °dH (267 ppm) "may make sense". Baxi wants the sealed heating circuit filled only from an unsoftened supply.

Pressure is the other everyday question. Most makers ask for about 1 to 1.5 bar with the system cold, rising to no more than about 2.5 bar when hot. The combi boilers page covers scale, the boiler pressure page covers topping up from the user manual, and the heating hub gathers the rest, including powerflushing. Anything inside a gas boiler is work for a Gas Safe registered engineer.

Who fixes a leak on the pipe outside?

That depends on which side of your boundary the leak is. Portsmouth Water owns the main and the communication pipe up to the boundary or its stop tap; from there the supply pipe into the house, and every pipe indoors, belongs to the owner, as Ofwat also sets out. The company says around 38% of leaks happen on customers' pipes and plumbing.

Portsmouth Water's leaks page offers £100 towards repairing a leaking supply pipe, or £200 towards replacing the whole of it, if the job is done within 30 days of the leak being found. Metered customers can ask for a leak allowance if the repair is done within 60 days, once in five years. The leaks page walks through who pays, burst pipes covers the stop tap and thawing, and water meters explains reading yours.

Which water rules apply to plumbing work?

The Water Supply (Water Fittings) Regulations 1999 apply to every fitting connected to the mains: nothing may be installed in a way that causes waste, misuse or contamination, and fittings must be of an appropriate quality and standard. Some jobs need notice to the water company first, among them a bath over 230 litres, a pump drawing more than 12 litres a minute and any reverse osmosis unit. Breaking the rules can bring a fine of up to level 3 on the standard scale.

An approved contractor, such as a plumber on the WaterSafe register, can certify the work and is exempt from notice for some items. Gas work is separate: anyone doing it must be competent, and anyone doing it as a business must be Gas Safe registered, so treat anything inside a gas appliance as an engineer's job. The water regulations page lists every notifiable job, and unvented cylinders covers Approved Document G's safety rules for hot water storage.

What do landlords have to check?

Gas first: every gas appliance and flue needs a safety check by a Gas Safe registered engineer at intervals of not more than 12 months, the record kept for 2 years and a copy given to existing tenants within 28 days. A carbon monoxide alarm is required in any room used as living accommodation that holds a fixed combustion appliance other than a gas cooker, a rule in force since 1 October 2022 with penalties of up to £5,000.

The HSE says landlords must assess the legionella risk, though testing is "not usually required" for domestic systems. Section 11 of the Landlord and Tenant Act 1985 makes the landlord keep the installations for water, gas, sanitation, space heating and hot water in repair. The landlords page sets out each duty with its source, and the pipes hub links the leak and drain pages that tenants ask about.

Further questions

Start here

• Water and limescale: hardness to filtersSection
• Boilers and hot water in hard-water HampshireSection
• Leaks, pipes and the water rulesSection
• Landlord gas safety and water dutiesLeaks, pipes and rules