Local Guide

London Water Quality 2026

Is Your Tap Water Safe? Complete Borough-by-Borough Guide

By Keith Wilks•Updated January 17, 2026•10 min read

Quick Summary: London Tap Water

Safe to Drink

Meets all UK standards

Very Hard

280-350mg/L typical

Chlorinated

For disinfection

Living in London and wondering about your tap water? You're not alone. With Thames Water regularly in the news—from sewage spills to infrastructure issues—it's natural to question what's actually coming out of your tap.

Here's the good news: London tap water is safe to drink. It meets all UK and EU drinking water standards, and Thames Water conducts over 500,000 tests annually. But "safe" doesn't mean "perfect"—London water has some characteristics that many residents find frustrating.

In this guide, I'll break down exactly what's in London's water, how it varies by borough, and whether you should consider filtering it.

What's Actually in London Tap Water?

The Good

Meets All Safety Standards
99.96% compliance with DWI regulations
No Added Fluoride
Unlike some UK regions
Mineral-Rich
Calcium and magnesium (from hardness)
Extensively Tested
500,000+ tests per year

The Concerns

Very Hard Water
Causes limescale buildup
Chlorine Taste/Smell
Added for disinfection
Potential Lead (Old Properties)
From pre-1970s pipes
Trace PFAS Detected
Within legal limits but present

Water Hardness by London Borough

Borough	Hardness	Rating	Main Source
Westminster	320mg/L	Very Hard	Thames/Aquifer
Tower Hamlets	310mg/L	Very Hard	Thames/Aquifer
Camden	305mg/L	Very Hard	Thames/Aquifer
Hackney	315mg/L	Very Hard	Thames/Aquifer
Islington	300mg/L	Very Hard	Thames/Aquifer
Southwark	295mg/L	Very Hard	Thames/Aquifer
Lambeth	290mg/L	Very Hard	Thames/Aquifer
Greenwich	285mg/L	Hard	Thames
Lewisham	280mg/L	Hard	Thames
Croydon	295mg/L	Very Hard	Aquifer
Bromley	290mg/L	Very Hard	Aquifer
Richmond	275mg/L	Hard	Thames

Data based on Thames Water reports. Check your exact postcode at Thames Water's water quality checker

Lead Pipes: The Hidden Risk in London Properties

Thames Water has removed lead from their mains network, but if your property was built before 1970, you may still have lead pipes connecting your home to the mains or within your internal plumbing.

How to Check for Lead Pipes:

Look at the pipe under your kitchen sink where it enters the property
Lead pipes are dull grey (not shiny like copper or plastic)
Try scratching with a coin—lead is soft and will scratch easily
Lead pipes often have rounded, bulbous joints

High-risk London areas include Victorian and Edwardian properties in boroughs like Islington, Camden, Hackney, and parts of South London. If you're in a pre-1970s property, I'd strongly recommend either testing your water or using a filter certified for lead removal.

Full Lead Pipe Guide Best Filters for Lead

Thames Water: The Bigger Picture

Let's address the elephant in the room: Thames Water has been in the news for all the wrong reasons—sewage spills, debt problems, potential nationalisation. Does this affect your drinking water quality?

The short answer is no. Drinking water treatment and sewage handling are separate operations. Thames Water's drinking water quality remains excellent (99.96% compliance) even as their sewage infrastructure struggles. The Drinking Water Inspectorate (DWI) monitors this independently.

That said, I understand the trust issue. When a company is clearly struggling with basic infrastructure, it's natural to question everything. If you want extra peace of mind, a home water filter gives you that final layer of control.

Do You Need a Water Filter in London?

You Probably DON'T Need a Filter If:

You're happy with the taste of your tap water
Your property was built after 1970 (no lead pipes)
You're not concerned about trace contaminants within legal limits

Consider a Filter If:

You dislike the chlorine taste or smell
You live in a pre-1970s property (potential lead pipes)
You want to remove PFAS/forever chemicals
You're pregnant or have young children (extra caution)
You want limescale-free water for drinking (not whole-house)

My Filter Recommendations for London

BEST FOR MOST LONDONERS

Waterdrop 10UA

£59.48

NSF 42/53 certified carbon block filter. Removes chlorine taste, lead, VOCs. Perfect for London's hard water. 12-month filter life.

Check Price

BEST FOR LEAD & PFAS

Waterdrop G3P600

£399

Tankless RO system removes 99%+ of ALL contaminants including lead, PFAS, fluoride, arsenic. Smart faucet shows filter life.

Check Price

Frequently Asked Questions

Is London tap water safe to drink in 2026?

Yes, London tap water is legally safe to drink and meets all UK and EU drinking water standards. Thames Water treats and tests it extensively. However, it's very hard (over 300mg/L calcium carbonate in most areas), contains chlorine for disinfection, and may pick up lead from old pipes in pre-1970s properties. Many Londoners choose to filter for taste improvement.

Why is London water so hard?

London's water is hard because it's drawn from chalk aquifers and the River Thames, which flows through limestone and chalk geology. As water passes through these rocks, it absorbs calcium and magnesium minerals. Most London boroughs have water hardness of 280-350mg/L (very hard), compared to the UK average of around 200mg/L.

Does London tap water contain lead?

London's mains water supply doesn't contain lead—Thames Water removed lead pipes from their network. However, if your property was built before 1970, you may have lead pipes connecting your home to the mains (the 'communication pipe') or internal lead plumbing. This is the main source of lead in London tap water. You can check by looking at pipes under your kitchen sink—lead pipes are dull grey and soft enough to scratch with a coin.

What is the water hardness in my London borough?

Most London boroughs have very hard water (280-350mg/L). Central and East London (Westminster, Tower Hamlets, Hackney) tend to be slightly harder than outer boroughs. You can check your exact postcode on Thames Water's website or use a home test kit. Hard water isn't a health risk but causes limescale buildup in kettles and appliances.

Should I filter my London tap water?

It depends on your concerns. For taste improvement and chlorine removal, a simple carbon filter (£50-100) is sufficient. If you have lead pipes, want to remove PFAS, or want to reduce limescale in drinking water, consider a reverse osmosis system. If you're happy with the taste and don't have lead pipes, filtering isn't necessary for safety.

Does Thames Water add fluoride to London water?

No, Thames Water does not add fluoride to London's water supply. Unlike some other UK regions (parts of the Midlands and North East), London water is not fluoridated. Any fluoride present is naturally occurring at very low levels (typically 0.1-0.2mg/L), well below the 1mg/L level used in fluoridated areas.

Not Sure What Filter You Need?

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