Unvented Hot Water Cylinder Service and Repairs in London

4.9 stars, 1,000+ reviews | G3 qualified | Fixed-price annual service | Same or next day | One-hour arrival window | Book online 24/7

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A specific one-hour arrival window is confirmed on every booking, so there is no need to wait in all day.

How much does an unvented cylinder service or repair cost in London?

An annual unvented hot water cylinder or Megaflo service from Silver Saints is a fixed price of £100 plus VAT in London, with no call-out fee, carried out by a G3-qualified engineer, and Saturday is charged at the same rate. Fault diagnosis and repair, where the cylinder has a problem rather than needing a routine service, is charged at £98 plus VAT per hour, with any parts and the likely cost explained and agreed before the work is done. A service takes around an hour for a typical Megaflo, and most common repairs, such as recharging the expansion vessel or replacing a relief valve, are completed within the hour.

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Why Silver Saints

Here is why London customers have booked Silver Saints for unvented cylinder service and repairs since 2008.

• 4.9 stars from over 1,000 Google reviews
• 5 stars on Trustpilot and Checkatrade
• G3-qualified engineers for unvented and pressurised cylinders
• £5 million public liability insurance
• Operating since May 2008
• All work guaranteed against faulty workmanship
• A specific one-hour arrival window on every booking

Need an unvented cylinder service or repair in London? We can often come today or tomorrow.

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Why must an unvented cylinder be serviced by a G3-qualified engineer?

By law, any unvented or pressurised hot water cylinder over 15 litres in London may only be worked on by a G3-qualified engineer, and every Silver Saints engineer who attends an unvented cylinder holds that qualification. An unvented cylinder stores water under mains pressure, which is what gives strong flow to every tap and shower in the house at once, and that pressure is also why the safety devices matter: a pressurised cylinder with a failed safety valve does not simply leak, it can discharge under force. The annual service exists to confirm the safety valves, the expansion provision and the discharge route all work correctly, and it is also what keeps most manufacturer warranties valid, including Heatrae Sadia Megaflo.

What is included in an unvented cylinder service?

A Silver Saints annual unvented cylinder service in London is a fixed 15-point check carried out by a G3 engineer. It covers removing and cleaning filters and strainers, checking the cylinder for leaks or damage, checking and topping up the expansion vessel air charge or the float-operated valve, resetting the expansion gap where fitted, and manually operating both the expansion relief valve and the temperature and pressure relief valve to confirm each opens, closes and reseals correctly. The engineer also checks the discharge pipes and termination position, the temperature settings and controls, the sacrificial anode, the heat exchanger in hard water areas where accessible, the water pressure downstream of the pressure reducing valve, and the flow rates at the taps, before explaining the work and completing a service record.

Why is my tundish dripping or discharging water?

A dripping or discharging tundish is the most common unvented cylinder symptom in London homes, and it almost always means the expansion vessel air charge has been lost or a safety valve is starting to fail. The tundish is the visible air gap on the discharge pipe near the cylinder, and it should be dry in normal use, so water running from it tells the engineer the cylinder can no longer absorb the expansion of heated water and is dumping the excess. A Silver Saints G3 engineer will recharge the expansion vessel or reset the internal air gap, and test the relief valves to confirm each reseals correctly. Left alone, a discharging tundish can run continuously and, if a valve fails outright, cause real water damage, so it is worth booking promptly.

Common unvented cylinder and Megaflo faults we repair

Silver Saints repairs the full range of unvented cylinder faults in London, and the symptom usually points to the cause. A drop in hot water pressure or flow is typically a failing pressure reducing valve or a waterlogged expansion vessel. Lukewarm water, or no hot water on an electric cylinder, usually points to a failed immersion heater or thermostat, while no hot water on an indirect cylinder points back to the boiler or the motorised valve. Water escaping when the system is not in use points to a relief valve not reseating. We work on all the major brands, including Heatrae Sadia Megaflo, Gledhill and the other common unvented makes found in London homes, with parts and cost agreed before any repair.

Unvented systems in London properties

Unvented cylinders and Megaflo systems are the standard in larger London homes and high-specification flats, because they deliver mains-pressure hot water to several bathrooms at once without a loft tank. That suits townhouses across Kensington, Chelsea and Westminster, and modern new-builds across Nine Elms, Battersea and Canary Wharf. It is also why a neglected unvented system is a serious risk in these properties: a failed safety valve or a split cylinder forces water out under pressure and can track through floors and ceilings, so an annual G3 service is cheap insurance against a large repair bill. Older conversions sometimes have the cylinder boxed into a tight airing cupboard, which the engineer works around as part of the visit.

For landlords and letting agents

Silver Saints services and repairs unvented cylinders for landlords and letting agents across London, and an annual cylinder service sits naturally alongside a landlord gas safety certificate and a boiler service in the same visit. We arrange access directly with your tenant or collect keys from your agent, and you can read more about our landlord services, including the pre-approved spend limit that lets routine work go ahead without quote-chasing.

Combine your cylinder service with other work in one visit

Because every Silver Saints engineer is multi-trade, an unvented cylinder service or repair can be combined with other work in the same London visit with no second call-out fee. Customers commonly pair a cylinder service with an annual gas boiler service, a landlord gas safety record, bleeding or balancing radiators, or sorting low system pressure on the heating side, all under one appointment.

Unvented cylinder service and repair FAQs

Can you service or repair my unvented cylinder in London today?

Silver Saints offers same-day and next-day unvented cylinder and Megaflo appointments across London, subject to G3 engineer availability. Call 0207 0999 199 or book online at bookings.silversaints.com and the team will confirm the earliest slot for your postcode.

How much does an unvented cylinder service or repair cost in London?

An annual unvented hot water cylinder or Megaflo service from Silver Saints is a fixed price of £100 plus VAT with no call-out fee, and fault diagnosis and repair is charged at £98 plus VAT per hour. Saturday work is charged at the same weekday rate.

Why is my tundish dripping or discharging water?

A dripping or discharging tundish usually means the expansion vessel air charge has been lost or a safety valve is failing. A Silver Saints G3 engineer recharges the expansion provision and tests the relief valves, because a tundish should be dry in normal use, and a discharging one can cause water damage if ignored.

Why has my unvented hot water pressure dropped?

A drop in unvented hot water pressure or flow in a London home is typically caused by a failing pressure reducing valve or a waterlogged expansion vessel, both of which a Silver Saints G3 engineer can diagnose and repair, usually within the hour.

Do you service and repair Megaflo cylinders?

Yes, Silver Saints services and repairs Megaflo cylinders across London, along with Heatrae Sadia, Gledhill and the other common unvented makes found in London homes. Megaflo is one of the most common unvented brands we work on.

Does an unvented cylinder have to be serviced by a G3 engineer?

Yes. By law, any unvented or pressurised hot water cylinder over 15 litres may only be serviced or repaired by a G3-qualified engineer, and every Silver Saints engineer who attends an unvented cylinder in London holds that qualification.

How often should an unvented cylinder be serviced?

An unvented hot water cylinder should be serviced once a year to check the safety valves, the expansion provision and the discharge route. Annual servicing is also required to keep most manufacturer warranties valid, including Heatrae Sadia Megaflo.

Can you combine a cylinder service with a boiler service or gas safety certificate?

Yes. Because Silver Saints engineers are multi-trade and G3 qualified, an unvented cylinder service can be carried out in the same London visit as a gas boiler service or a landlord gas safety certificate, with no second call-out fee.

In summary

Silver Saints unvented hot water cylinder service and repairs is a G3-qualified service for pressurised cylinders and Megaflo systems in London homes. The annual service is a fixed 15-point check of the expansion vessel, the relief valves, the discharge route and the controls, and a repair diagnoses and fixes faults such as a dripping tundish, lost hot water pressure, a failed immersion or a leaking valve. It is carried out Monday to Saturday, 8am to 5pm, at a fixed price of £100 plus VAT for the annual service, with repairs at £98 plus VAT per hour. Silver Saints is rated 4.9 stars on Google from over 1,000 reviews, is fully insured, and has worked on London hot water systems since 2008. To book, call 0207 0999 199 or  make an online booking.