Hot water cylinders in Broxbourne and nearby towns

What is a hot water cylinder?

A hot water cylinder is an insulated tank, often in an airing cupboard, that stores hot water for the taps and shower. A boiler heats it through a coil inside, and many also have an electric immersion heater as a backup or as the main source of heat.

Homes with a combination boiler usually have no cylinder, because that boiler heats water as you use it. A cylinder tends to be found in houses with a system or regular boiler, or in homes where the water is heated electrically.

What is the difference between vented and unvented cylinders?

A vented cylinder is fed from a cold water tank in the loft. The water is at low pressure and an open pipe runs up to the tank, which is why hot taps and showers can feel weak.

An unvented cylinder is fed straight from the mains, so you get stronger flow and no loft tank. It is sealed, so it has safety devices, including a temperature and pressure relief valve and a discharge pipe, which must never be blocked or altered.

Who is allowed to fit an unvented cylinder?

Unvented cylinders store water under pressure and can be dangerous if they are installed or maintained wrongly. In England the work is covered by the Building Regulations, with guidance in Approved Document G, and must be done by a suitably qualified installer who is competent to install them. It needs to be notified to building control, which a registered installer can do through their Competent Person Scheme.

Ask to see evidence of the qualification before you agree, and ask for the paperwork when the job is done. If a boiler is replaced at the same time, any gas work needs a Gas Safe registered engineer. If you ever smell gas, call the National Gas Emergency Service on 0800 111 999.

What are the signs my cylinder has a problem?

• hot water that runs out quickly, or never gets hot
• water dripping from the cylinder, its pipes or the discharge pipe
• a loud banging, humming or rumbling from the cupboard
• a lot of limescale, or discoloured water from the hot tap
• a cylinder that is old, with a dented, stained or rusty casing

Some of these are minor, such as a worn thermostat or a failed immersion heater. Others, such as a leak from the body of the tank, mean it has reached the end of its life.

What should I do if my cylinder is leaking?

Turn off the water supply to the cylinder, and switch off the immersion heater at its switch and at the consumer unit if you can safely reach it. Keep water away from electrics and do not touch an immersion heater or its wiring if it is wet.

If you have an unvented cylinder and water is running steadily from the discharge pipe, or the cylinder seems to be overheating, keep clear and call 999 if anyone is in danger. Never tamper with the relief valve.

Should I repair or replace it?

Parts that can often be changed include immersion heaters, thermostats and valves. If the tank itself is leaking, replacement is the usual answer, since the body cannot be mended reliably.

A cylinder that is decades old, badly scaled or poorly insulated may be better replaced even if it still works. Hard water, which is the norm across Hertfordshire, speeds up scale on heating elements and coils.

Can I swap one type of cylinder for another?

Often, but it is a bigger job than a straight swap. Changing from vented to unvented can remove the loft tank and improve pressure, but your pipework must be able to take mains pressure, and an old system may need parts replaced.

Cylinders are available in different sizes, so work out how much hot water your household uses. A plumber can talk through the options. Think about where it will fit, what weight the floor can bear and whether you want to keep the old airing cupboard shelving.

What about servicing?

An unvented cylinder usually needs a periodic check of its safety devices, and the maker's instructions will say how often. Keeping the paperwork from installation together helps whoever services it.

Vented cylinders have fewer safety parts, but it is sensible to check the insulation, the immersion heater and the pipes round the cylinder from time to time.

What should I include in my enquiry?

• your postcode, so we can check whether a plumber covers you
• whether you want a repair, a replacement or advice
• the type of cylinder, if you know it, and whether there is a loft tank
• how the water is heated: boiler, immersion heater or both
• the symptoms, such as a leak, no hot water or noise
• the age of the cylinder, if you know it

What happens after I send it?

With your consent, we pass your enquiry to one local plumber, if one covers your postcode, and to nobody else. If nobody does, we tell you. The plumber contacts you to talk about the job, and you agree the details and cost with them directly. Sending an enquiry is free and you are not committed to anything.