Outside tap covers: how to protect a garden tap from frost

What an outside tap cover actually does

Covers come as soft insulated pouches that pull over the tap and tie or clip at the back, and as rigid foam boxes that fit over the tap and its wall plate. Both work the same way: they trap still air around the tap and slow down heat loss. That buys time on a cold night when the tap is still connected to a live supply, because mains water moving through the pipes behind it carries a little heat.

What a cover cannot do is keep a tap above freezing through several days of frost. Once the water in the tap body and the short pipe behind it has cooled to 0°C, it freezes whether it is covered or not. Ice expands as it forms, and that pressure is what splits the tap body, pushes the washer out or cracks a fitting inside the wall.

A cover is the last step of winter-proofing, not the whole job.

How to winter-proof an outside tap, step by step

Do this in late autumn, before the first hard frost. It takes about 10 minutes if the tap has an isolating valve.

• Disconnect the hose. A hose left attached holds water against the tap outlet and can freeze back into it. Drain the hose and store it indoors.
• Find the isolating valve for the outside tap indoors. It is usually on the pipe where it leaves the kitchen, utility room or garage, often under the sink next to the washing machine valves. It may be a small lever valve or a screwdriver-slot valve.
• Turn the isolating valve off. A lever valve is off when the handle is across the pipe; a slotted valve is off when the slot is across the pipe.
• Open the outside tap fully and leave it running until it stops. If the pipe has a drain-off point next to the isolating valve, open it too so the section in the wall empties.
• Close the outside tap gently, or leave it slightly open if the manufacturer suggests it, then fit the cover so it sits snug against the wall.
• Lag any visible pipe between the wall and the tap with foam pipe insulation designed for outdoor use, and seal the hole where the pipe passes through the wall to stop draughts reaching it.

Never pour boiling water over a frozen tap or use a naked flame, heat gun or blowtorch on it. Sudden heat can crack a frozen tap body or a soldered joint, and a flame near a wall or timber is a fire risk.

If there is no isolating valve

A lot of older London houses and conversions have outside taps teed straight off the rising main with no separate valve. You cannot drain the tap without turning off water to the whole house, and the pipe inside the wall stays full all winter.

In that case a cover and lagging are the best you can do for now, and it is worth having an isolating valve fitted before the weather turns. It is a small job, and it also means that if the tap ever does split, you can turn it off without losing water to the house.

If an outside tap is being replaced or moved anyway, consider a tap with built-in backflow protection. Under the Water Supply (Water Fittings) Regulations 1999, an outside tap should have suitable backflow protection, typically a double check valve, so that water from a hose cannot be drawn back into the drinking supply. Our guide to garden hose backflow covers what is appropriate for different uses.

Signs the tap has already frozen or split

Frozen taps rarely show damage until the thaw, when water can flow again. Check an outside tap after the first cold spell rather than waiting for spring. If it gives no water when you reopen the valve in spring, our guide to an outside tap not working goes through the likely causes.

• No water from the outside tap when the rest of the house has normal pressure: it may be frozen, or the isolating valve is still off.
• Water dripping or spraying from the tap body, spindle or under the wall plate when the supply is turned back on.
• Damp patches on the inside wall behind the tap, in the kitchen cupboard, or on the ceiling below if the pipe runs through a floor void.
• The water meter moving with every tap in the house turned off.
• A cracked or bulged tap body, or a split visible in the pipe where it leaves the wall.

What to do if it bursts

If water is leaking from the tap or wall, turn off the isolating valve if there is one. If not, turn off the main stopcock, usually under the kitchen sink or where the supply pipe enters the house. Open the cold taps inside to drain the pipes, and move anything that could be damaged away from a wet wall.

A split in the pipe inside the wall can soak into plaster, floorboards and the room below before anyone notices, so it is worth getting it looked at promptly even if the leak outside seems small. Our guide to an outside tap leaking after frost explains how the tap, the concealed connection and the pipe are checked.

Loyal Plumbers repairs and replaces outside taps and burst pipes across London and everywhere inside the M25, 24 hours a day, with 10 vans on the road. Our call-out charge is £60. Call 020 4652 8585, or send an enquiry saying where the tap is and whether water is getting inside.