What Is an Airing Cupboard? What Is Inside and What to Check

Why it is called an airing cupboard

"Airing" is the old word for the last stage of drying, when laundry that feels dry is left somewhere warm so the remaining damp can escape before it goes into a drawer. A copper hot water cylinder that was lightly insulated, or not insulated at all, made the cupboard around it the warmest, driest place in the house, so builders put slatted shelves above it and the name stuck.

Modern cylinders are far better insulated, so the cupboard is not as warm as it was in a 1970s house. It is still usually the warmest cupboard you have, and a noticeably hot airing cupboard is often a sign that the cylinder or its pipes are losing more heat than they should.

What is inside an airing cupboard on a tank fed system

Most older London houses and conversions have a vented, or tank fed, cylinder. It is fed by gravity from a cold water tank in the loft, and the pressure at the taps depends on how high that tank sits. Inside the cupboard you will usually find:

• The cylinder itself, normally copper, either bare or covered in a factory foam layer or a fitted jacket.
• An immersion heater, an electric element screwed into the top or side of the cylinder, with its own switch on the wall outside or just inside the cupboard.
• A cylinder thermostat, a small dial strapped to the side of the cylinder a third of the way up, which tells the boiler when the water is hot enough.
• One or two motorised valves on the pipes from the boiler, small boxes with a lever on the side, which open to send boiler water to the cylinder or the radiators.
• On some systems the central heating pump, which is often fitted in the airing cupboard rather than inside the boiler.
• A cold feed pipe coming down from the loft tank into the bottom of the cylinder, usually with a gate valve on it, and a vent pipe rising from the top back up to the loft.

What is inside if you have an unvented cylinder

An unvented cylinder is fed straight from the mains, so it runs at mains pressure and needs a set of safety devices that a tank fed cylinder does not. The loft tank is gone and the airing cupboard gets busier. As well as the cylinder, immersion heater and thermostat, expect to see:

• An inlet control group on the incoming mains pipe, a cluster of brass valves including a pressure reducing valve and a strainer.
• An expansion vessel, a round metal tank usually white, blue or grey, mounted on the wall or on the cylinder, which absorbs the water that expands as it heats.
• A temperature and pressure relief valve near the top of the cylinder, the last line of defence if the water gets too hot or the pressure too high.
• A tundish, a small open funnel with a gap in the pipe, where any water discharged from the relief valves becomes visible before it runs away to a drain.

An unvented cylinder must be fitted and maintained by someone qualified to work on it, which is what the G3 in our name refers to. You can look and report what you see. Do not adjust or dismantle the valves, the expansion vessel or the relief valve yourself.

And if you have a combi boiler?

A combi heats water on demand, so it has no cylinder and, strictly, no airing cupboard. In a lot of homes that changed to a combi the old airing cupboard is still there, empty except for a few capped pipes, or it has been turned into shelving. If you are thinking about going the other way, or about removing your cylinder to fit a combi, our guide on converting to a combi boiler covers what you gain and what you give up.

Warning signs worth acting on

Most cylinder faults show up in the airing cupboard before they show up anywhere else. Open the door once a month or so and look for these:

• Water on the floor, damp shelves, green or white crust on pipe joints, or drips from the bottom of the cylinder. Our guide on a hot water cylinder leaking explains how to tell a loose joint from a failing tank.
• Water running or dripping into the tundish on an unvented cylinder. It means a relief valve has opened. Read our page on a tundish dripping before doing anything else.
• A hissing, banging or boiling noise from the cylinder, which can mean the water is overheating. Our hot water cylinder making noise page covers the causes.
• A cupboard that feels much hotter than usual, or pipes too hot to touch, which can point to a stuck thermostat or valve.
• A burning smell, scorched plastic or a discoloured switch near the immersion heater. Switch it off at the wall and have the wiring checked.

What you can safely keep in an airing cupboard

Towels, bedding and clothes are fine on the shelves, which is what the cupboard is for. The problems start when it becomes general storage. Keep a clear path to the immersion heater switch, the valves and the tundish, because anyone who needs to turn the water off in a hurry has to reach them, and an engineer needs to see them.

Do not pack laundry or boxes tightly against the cylinder controls, the immersion heater cover or the wiring, and do not keep paint, aerosols, solvents or cleaning products in there. Avoid hanging dripping wet washing directly on an electrical connection or the expansion vessel. If you have an unvented cylinder, make sure nothing blocks your view of the tundish, because water running into it is the warning you need to see.

Should an airing cupboard be warm?

A little warm is normal. Very hot is money leaking away. Heat that warms your towels is heat you paid to put into the water, and it is lost all day and all night. If the cylinder is bare copper or its jacket is thin, a fitted cylinder jacket is one of the cheapest improvements you can make, and our guide to a hot water cylinder jacket explains what to buy. Insulating the first metre or two of pipe coming off the cylinder helps too, and our page on insulating hot water pipes covers how.

If you would like to keep the cupboard warm enough to air laundry, a well insulated modern cylinder will still take the chill off it. It just will not bake your towels the way an old copper tank did.

When to call an engineer

If you see water where it should not be, water in the tundish, a cylinder that is noisy or too hot, or hot water that has stopped altogether, it is worth a visit before a small fault becomes a flooded landing. Our engineers work on both tank fed and unvented cylinders every day and carry the common valves and elements. Call 020 4652 5111 or send an enquiry with a photo of the inside of your airing cupboard, which often tells us what we are dealing with before we arrive. Our rate is on the pricing page and agreed before we attend.