Hot water cylinders
Hot water cylinder repairs and servicing in Bristol
Hot water cylinders in Bristol suffer from limescale, because Bristol Water's supply is moderately hard to very hard. Scale coats immersion heater elements and furs up the safety valves on unvented cylinders. We repair and service unvented and vented cylinders and replace immersion heaters, and in England unvented work must be done by someone competent under Building Regulations G3.
Photo for illustrationWhen to call
You need this when
- No hot water, or it runs cold quickly
- Water dripping from the pipe below the cylinder safety valves
- The immersion heater trips the electrics or will not heat
- The cylinder is making rumbling or cracking noises
- Water around the base of the cylinder
- Your unvented cylinder has not been serviced for over a year
The visit
What happens, step by step
- 01
Check the system
We find out what you have: unvented, vented with a loft tank, or a thermal store.
- 02
Find the fault
We test the immersion, thermostats, motorised valve, safety valves and expansion vessel.
- 03
Repair or service
We replace failed parts, descale where needed and reset pressures.
- 04
Safety check
On unvented cylinders we test the relief valves and check the discharge pipe runs safely.
- 05
Record
We fill in the service record, which most cylinder warranties require.
Unvented or vented: which do you have
A vented cylinder is fed by a cold water tank in the loft and works by gravity. You will see the tank in the loft and a pipe looping over the cylinder. Many interwar homes in Henleaze, Westbury on Trym and Knowle still have this setup.
An unvented cylinder is fed straight from the mains, with no loft tank. It has a bundle of valves on the cold pipe, an expansion vessel and a pipe called a tundish that carries any discharge to a safe place outside. These are common in larger homes and newer builds, and in many Clifton and Redland conversions.
Unvented cylinders store hot water under pressure, so they have safety devices. In England, Building Regulations Part G3 requires them to be installed by a competent person and notified to building control. Approved Document G sets this out. Ask anyone working on yours to show you their unvented qualification.
What Bristol's hard water does to a cylinder
Bristol Water says its water is moderately hard to very hard and that scaling of hot water systems is one of the main effects. Inside a cylinder, scale builds up on the immersion element and the coil. That makes heating slower and can burn the element out.
On an unvented cylinder, scale can stop the pressure reducing valve and the relief valves working properly. A furred valve that weeps is the most common reason for water dripping from the tundish.
Bristol Water suggests keeping hot water below 60 C to reduce scale. Be careful with this on a stored system. Stored hot water is normally kept at 60 C to control legionella bacteria, so we protect against scale in other ways, such as a scale reducer on the cold feed, rather than turning the cylinder down.
Immersion heaters
An immersion heater is an electric element in the cylinder. When it fails, the usual causes are a burnt out element, a failed thermostat or the safety cut out tripping. In Bristol, scaled elements are common. Replacing the element is a plumbing job because the cylinder has to be drained. A like for like swap on the existing circuit is usually not notifiable, but a new circuit is electrical work under Part P and needs a registered electrician.
Signs your cylinder needs attention
Most cylinder problems give a warning first. Water dripping from the tundish or the pipe outside means a safety valve is opening, which needs checking soon. Hot water that runs cold fast can mean a scaled coil or a failed motorised valve. Rumbling or cracking from the cylinder often means scale on the element. Damp patches under an airing cupboard can be a weeping joint on the cylinder pipework.
If the cylinder itself is leaking from the body, it usually needs replacing rather than repairing. When you replace a cylinder, it is worth thinking about the whole system. Some owners switch from a vented cylinder and loft tank to an unvented cylinder for better pressure. Our post on taking out the loft water tank explains what that involves.
Price
What affects the price
The price depends on the type of cylinder, the part that has failed and whether the cylinder needs draining. Older cylinders can be heavily scaled, and some parts are brand specific.
| What | Price |
|---|---|
| Unvented cylinder service | price confirmed after a look at the job |
| Immersion heater replacement | price confirmed after a look at the job |
| Safety valve, expansion vessel or motorised valve repair | quote on survey |
| Cylinder replacement | quote on survey |
No prices are shown on this site. Every job is priced after a look at it, by photo or a visit.
Questions
Hot water cylinders: what people ask
How often should an unvented cylinder be serviced?
Most manufacturers ask for a yearly service to keep the warranty valid. In hard water areas like Bristol, the safety valves benefit from regular checks.
Why is water dripping from the pipe under my cylinder?
On an unvented cylinder, that usually means a safety valve is letting water through, often because of scale or a failed expansion vessel. Get it checked soon.
Can I turn my cylinder down to stop limescale?
Stored hot water is normally kept at 60 C to control legionella. Ask a plumber about scale protection rather than turning it down.
Is an immersion heater a plumber or electrician job?
Replacing the element is usually a plumbing job because the cylinder is drained. New wiring or a new circuit is a job for an electrician under Part P.
Where
Hot water cylinders across Bristol
Hot water cylinders
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