No hot water
Often a zone valve, cylinder thermostat or immersion heater fault, rather than the cylinder itself.
Hot water cylinders
Hot water cylinders, done safely.
Repairs, replacements and new installations for vented and unvented hot water cylinders, including immersion heaters, thermostats, expansion vessels and safety valves.
Gas Safe registeredG3 unvented qualified [CONFIRM]Legionella-safe settings
Symptoms
Signs your cylinder needs attention
Runs out too fast
A failed element, a thermostat set too low, or a cylinder too small for the household.
Water from the tundish
On an unvented cylinder, water from the tundish means a safety device is working. Turn off the heat sources and call.
Leaking cylinder
Leaks from the body usually mean corrosion and replacement. Leaks at fittings can often be repaired.
Poor shower pressure
Vented (gravity) systems are limited by loft tank height. Unvented cylinders run at mains pressure.
Noisy heating up
Limescale on the coil or element, common in hard-water areas like Wiltshire.
The science
Hot water safety, by the numbers
Stored hot water must be hot enough to control Legionella bacteria, and unvented cylinders must be installed and maintained by competent people.
60°C
Minimum storage
Stored hot water should be kept at 60°C or above to control Legionella bacteria.
Source: HSE ACOP L8 and HSG274 Part 220–45°C
Danger zone
The temperature range in which Legionella bacteria multiply most readily.
Source: HSE ACOP L850°C
At the tap
Hot water should reach at least 50°C at outlets, usually within one minute of running.
Source: HSE HSG274 Part 2Part G3
Unvented law
Unvented cylinders must be installed by a competent person and the work notified to building control.
Source: Building Regulations, Approved Document GHow an unvented cylinder stays safe
An unvented cylinder holds hot water at mains pressure, so it has layers of protection: a pressure reducing valve, an expansion vessel to absorb the water's expansion as it heats, and a temperature and pressure relief valve that opens before things get dangerous. The discharge goes through a tundish so you can see when a device has operated. That's why the annual service matters.
Hot enough, not too hot
Storing at 60°C controls Legionella, but water that hot can scald in seconds. The answer is to store hot and blend down at the outlet with thermostatic mixing valves where needed, especially for baths used by children or older people.
Compare
Vented, unvented or combi?
The right choice depends on your home, your bathrooms and your incoming water supply.
| Vented cylinder | Unvented cylinder | Combi boiler | |
|---|---|---|---|
| Pressure | Gravity-fed from a loft tank | Mains pressure | Mains pressure |
| Stored hot water | Yes | Yes | No, heated on demand |
| Several showers at once | Yes, at lower pressure | Yes, if the mains supply is strong | Limited by flow rate |
| Loft tank needed | Yes | No | No |
| Annual safety check | Recommended | Recommended by manufacturers | Boiler service |
| Best for | Low mains pressure areas | Larger homes, 2+ bathrooms | Smaller homes, 1 bathroom |
FAQs
Hot water cylinder questions
Water is dripping from the tundish on my unvented cylinder. What should I do?
That's a safety device telling you something is wrong, often a failed expansion vessel or relief valve. Turn off the boiler and immersion heater, don't touch the discharge pipe (it can be very hot), and call an engineer.
Should I choose an unvented cylinder or a combi boiler?
A combi heats water on demand and suits smaller homes with one bathroom. An unvented cylinder stores hot water at mains pressure and suits homes with more than one bathroom used at the same time, provided the incoming water supply is strong enough. We test your flow and pressure before recommending one.
How often should an unvented cylinder be serviced?
Manufacturers recommend once a year. The service checks the expansion vessel charge, the pressure reducing valve and the temperature and pressure relief valve, and is often required to keep the warranty valid.
Can you convert my old tank system to unvented?
Often, yes. It frees up the loft and the airing cupboard and gives mains-pressure showers. It depends on your incoming mains flow and pressure, which we test first.
Why does my hot water run out quickly?
Common causes are a faulty cylinder thermostat, a failed immersion element, a sticking zone valve, or a cylinder that's simply too small for the household.
Sources and standards referenced
- HSE Approved Code of Practice L8, Legionnaires' disease: the control of legionella bacteria in water systems
- HSE HSG274 Part 2, hot and cold water systems
- Building Regulations 2010, Approved Document G (G3: hot water storage)
Areas covered
Hot water cylinder services across Trowbridge and West Wiltshire
Based in Trowbridge, covering a 25-mile radius. Not sure if you're covered? Call and ask.
TrowbridgeBathBristolSwindonFromeYeovilBradford on AvonMelkshamWestburyWarminsterDevizesChippenham