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South coast: hard water and sea air
Checked against its sources: Updated
South coast hard water comes from chalk: South East Water says most of its supply in southern England is hard, which matters for a boiler, and no official figure or rule on sea air was found.1 Check your postcode with your water company.1
- Covers
- Southern England for the water source; the sea-air note is about the documents read, not a rule.
- You
- Look up your hardness with your water company, and keep the flue terminal clear.
- A professional
- Scale treatment, and any question about flue or case materials at an exposed site.
1 Hard water
South East Water says most of the water it supplies in southern England comes from underground chalk aquifers, so it is hard, and that this can build up limescale in boilers and hot water pipes1. Its page gives no number and does not list towns, so no figure for Sussex is printed here. It sends customers to a postcode lookup1.
Southern Water's site, which could not be read, is not used here. Check which company bills you and ask it. The heating consequences are under limescale in a boiler and the rule under hard water treatment.
2 Sea air
No official figure exists in anything read for how far from the sea a boiler is affected, how much faster a flue wears or how often to service one on the coast. The user manuals from Worcester, Vaillant, Baxi, Main, Potterton, Glow-worm, Ideal and Viessmann were searched for coast, sea and salt air, and none of those words appears in that sense. Two Worcester oil boiler installation manuals and its flue kit instructions were also searched, with the same result3. This is a search of those documents, not of every manual in print.
The nearest wording is general. Worcester's flue kit instructions say combustion air must be free from chemically aggressive substances which can corrode the appliance3. Glow-worm's Energy7 lists sprays, solvents, chlorinated cleaning agents, paint, adhesives and ammonia compounds as causes of corrosion, without naming salt4. Neither says sea air qualifies. So this is not a confirmed rule, and an installer at an exposed site should be asked what the model's installation manual says. The usual boiler service advice applies.
Sources
- Water hardness, South East Water, undated help page read 3 November 2026.
- England's Part L dwellings guidance, 2021 edition, para 8.8 read 3 November 2026.
- Greenstar Oilfit flue kit instructions, Worcester, p3 read 3 November 2026.
- Energy7 combi operating instructions, Glow-worm, 02.03.2020, risk of corrosion section read 3 November 2026.