Hot Water Cylinder Replacement London

When you need a new hot water cylinder

Hot water cylinders in London typically run 20–30 years before the tank itself fails. Before then the symptoms creep in — a tundish drip that comes back six months after the last vessel swap, an immersion that trips an RCD on heat-up, brown water from the hot tap, scalding water that won't modulate, a recovery time that's doubled in a year, or a slow base leak staining the airing cupboard floor. Any one of these is a strong signal that the cylinder has reached the end of its economic life.

Cylinders made between 1990 and 2005 — early Megaflo CL Indirect, Gledhill EnviroFoam, Range Tribune Mk1 — are now well past the original 25-year warranty. By the time the expansion vessel, PRV and T&P have all been replaced twice, the smarter spend is a new cylinder with a fresh 25-year manufacturer warranty and modern factory foam giving roughly half the standing heat loss of pre-2010 units.

A like-for-like swap is the simplest case — same cylinder type, same size, same airing cupboard. A vented-to-unvented conversion is the bigger upgrade — removing the loft tank, fitting an expansion vessel, routing a new discharge pipe to outside, notifying Building Control. Both are routine work for a G3 qualified engineer and both are notifiable to Building Control under Approved Document G3 of the Building Regulations.

Cylinder types — which is right for your home?

Six cylinder types account for 95% of UK installs. The right one depends on mains pressure, gas / electric heat source, future heat-pump plans and how many bathrooms run simultaneously.

• Unvented (sealed, mains-pressure)

  The dominant new-install choice in London. No loft tank, mains-pressure feed to every outlet, strong shower flow. Requires a G3 ticket to install and an annual G3 service to maintain warranty. Brands: Megaflo, Telford, Joule, Gledhill, OSO, Kingspan.

• Vented (open-vent, loft tank fed)

  Older but still common in Victorian and Edwardian London stock. Fed by a cold-water storage tank in the loft, lower pressure but no G3 requirement. Cheaper to install in like-for-like swaps where the loft tank is staying put. Brands: Range, Telford Indirect, Albion Mainsaver.

• Direct (electric immersion only)

  Heated by one or two immersion elements — no boiler input. Used in all-electric flats, properties without gas, or as the primary store for a heat pump. Simpler safety devices, no primary coil. Often paired with Economy 7 or smart tariffs.

• Indirect (boiler-fed coil)

  The most common cylinder type behind a gas system boiler. The boiler heats a primary coil submerged in the stored water. Typically faster recovery than direct, more efficient on gas. Almost always fitted with a backup immersion for redundancy.

• Solar thermal twin-coil

  Has a second lower coil sized for a solar thermal array. Stores low-grade solar heat through the day, topped up by the boiler in the evening. Still relevant in London new-builds and listed buildings reluctant to add a heat pump.

• Smart cylinders (Mixergy, Tepeo, Sunamp)

  Top-down stratification and app control let smart cylinders heat only the volume you'll actually use in the next hour. Pairs with solar PV, octopus agile tariffs and home batteries. Premium price, real savings on electric-heated stores.

Hot water cylinder replacement cost London — 2026 prices

Every quote is a fixed figure in writing, given after a free on-site survey. No call-out fee on quoted installs, no parking add-ons, no surprise extras on the install day. Pricing below is for a like-for-like unvented replacement in a standard London flat or house. Vented swaps are £150–£250 lower. Direct (electric only) cylinders are £100 lower than indirect.

* All prices include VAT, cylinder, all parts, labour, removal & disposal of old unit, Building Regulations G3 notification, Benchmark commissioning and 12-month workmanship guarantee. Full price list on the pricing page. Megaflo Eco premium model: +£250. Direct (electric only) variants: −£100.

Sizing your new cylinder — bedrooms, bathrooms, occupants

Sizing follows the Hot Water Association rule: 35–45 litres per occupant, plus 60 litres per bathroom and an extra 50 litres for any property with a daily-used bath. Get it right and the cylinder recovers between uses; get it wrong and the family runs out of hot water on a school morning.

For HMOs, large family homes with simultaneous bathroom use and properties with freestanding baths over 200L capacity, we calculate sizing against the manufacturer's simultaneous-use flow curves rather than a rule of thumb. The on-site survey is the right place to settle this — every brand has subtly different recovery and stratification characteristics.

Our 5-step install process

Real London replacements — worked examples

Five anonymised cylinder replacements from the last twelve months across London. Every job is different — the cylinder type, the discharge route and the access drive the price more than the brand on the data plate.

Areas covered across London

Hot water cylinder replacement carried out across every London borough. Heaviest call volumes from Camden, Islington, Westminster, Hackney, Wandsworth, Kensington & Chelsea, Hammersmith & Fulham and Tower Hamlets.

Frequently asked questions