Industry insights

Is London Tap Water Still Safe To Drink?

2 min read

By Matt Stimpson |  Published

While London tap water may not be to everyone’s taste, it’s still perfectly safe to drink. In fact, London water is ranked among the best in the world for its quality. Drinking water safety standards in the UK are incredibly high, so it’s usually chemical or natural elements that can lead people to think it’s not safe. Let’s look at what happens to London tap water before you drink it.

Surface water vs groundwater

All London tap water is supplied by Thames Water. Covering 5,000 sq. miles, their water supply (and sewerage supply services) serves 15m people, reaching homes and businesses in Greater London and the Thames Valley, as well as parts of Surrey, Kent, Gloucestershire, and Wiltshire.

Much of the tap water supplied by Thames Water – around 70% of it – comes from stored surface water sources including reservoirs, while around 30% comes from groundwater sources deep underground (aquifers).

It then goes through a rigorous treatment and cleaning process, before supplying “an average of 2.7 billion litres to nearly ten million people across London and the Thames Valley” (Source). But while London tap water is safe to drink, what water safety is actually involved – and why does it taste different to other parts of the UK?

Testing for water safety

Carrying out over 500,000 tests each year, London tap water is subject to Water Supply Regulations that cover how your water looks, tastes, and smells, as well as its chemical content, treatment requirements, and monitoring arrangements. Included in each test are certain metrics that ensure water safety, including:

Total Dissolved Solids (TDS)

Dissolved solids in the water can include minerals like calcium, magnesium, sodium, chloride, and sulfate. The TDS level is a good indicator of how hard a region’s water is.

pH Value

pH values indicate how acidic or alkaline water is on a scale of 0 - 14 and tap water should have a pH level of between 6.5 to 8.5. With a low pH value, soft water will contain more metals than hard water.

Bacteria count

Harmful bacteria in water can include E.coli and coliform. Fortunately, the regulatory limit for bacteria in any drinking water is a reassuring 0 per 100ml.

Additional tests are also carried out on other chemical elements including, Chlorine, Lead, Fluoride, Mercury, Arsenic, Volatile Organic Compounds (VOCs), and Nitrates. But why does London tap water have such an odd taste? It’s notoriously hard water and when it comes up from those deep underground sources, it travels through soft, chalky limestone rock multiple times.

Surface water is naturally softer, but when combined with the naturally high mineral content of groundwater, the mineral content remains high, though that could actually give you an extra calcium boost. But if you really don’t like the tap water taste, there is a softer, better tasting alternative.

Water safety and great taste with Thirsty Work

Though connected directly to your mains tap water supply, all our mains fed water coolers feature advanced mechanical and carbon filtration systems for water safety, eliminating bad tastes. Both upright and counter-top models give you an economical and environmentally-friendly way to enjoy 100% filtered, great-tasting water at home or in the office.

For more information on all our mains fed water coolers and our fast same or next day deliveries across London and the south-east, call our customer service team today on 02080 498 501. Or email us at and you can start your free, no-risk 10-day, free trial to really taste the difference.

Your local Thirsty Work water delivery service covers all areas of North, South, East and West London, and surrounding areas. We aim to deliver water and cup supplies within 2 - 3 working days from your local delivery depot. 

Our head office for all enquiries is based in Exeter, but your local delivery depot is located in HEMEL HEMPSTEAD 
Thirsty Work Ltd
Unit 6 Fields End Farm
Pouchen End Lane
Hemel Hempstead

Call us on: 02080 498 501