Plumbing problems

The more diligent decorator takes off the radiator when lining or wallpapering a wall - making it easier to paper neatly behind the radiator position.

Just a few minutes’ work. The valves are turned off, and the radiator valves are disconnected from the radiator, the radiator contents - hopefully looking nice and clean - are emptied into a container, and the radiator set aside for reconnection later.

You would feel pretty confident that tightly shutting off the valves would reliably prevent any escape of water ... or would you?

There are two types of valve you might be attempting to turn off, a manual or thermostatic valve.

You would commonly find one valve fitted with a plastic cap able to actually turn off the valve – i.e. with a slot to fit over the valve spindle, but the other ‘lockshield’ valve fitted with a cap incorporating a circular housing – that would just revolve aimlessly when turned. The ‘lockshield valve’, is used when balancing the system. So take off both caps, and to make sure both valves are off, use a spanner if necessary to tweak them tight.

But a ‘thermostatic radiator valve’ (TRV) is fitted with a heat sensor. Such a valve senses the temperature in the room, and allows the valve to open, allowing hot water to enter and heat the radiator. You cannot reliably isolate such a valve by just turning down the temperature control. You will need to take off the temperature sensing head and secure the pressure pin with a dedicated manual locking nut. Otherwise (especially if you plan to remove the radiator for some time), you might have to consider taking the valve off and fitting a 15mm compression cap in its place. If you do not fit the locking nut, or safely cap off the pipe feed using a compression cap, you run the risk of the valve opening when there is a temperature drop in the ‘subject room’, which would cause a water escape. Some thermostatic valves actually have an ‘off ’ position, which may be safe in theory, but it is still a good idea to cap off the radiator connection or even drain down the system and cap off the supply. You also need to protect the valve from dust and dirt during the redecorating. You can either fit the patent dust cover, or fit a plastic bag around the valve, secured with tape.

But sadly, the Clapham household in our case study had not received this advice.

You might notice the inline service valve below the TRV. The plumber originally fitting the TRV had thought ahead – it would be possible to isolate the TRV with just a small turn of a screwdriver to turn off the service valve. But whoever took the radiator off did not realise the point of the service valve, and by failing to turn the on-off screw had caused thousands of pounds’ worth of devastation.

Manufacturers of TRVs are well aware of the risks of not properly shutting them down when a radiator is removed, and typically offer advice such as: ‘If the control head is used to close the valve, there is a danger of water damage if the temperature falls and the valve reopens unexpectedly.’

Thousands of pounds’ worth of damp remediation for the cost of one radiator blanking-off cap.

Figure 1: Somebody removed a radiator, but didn’t realise that this type of valve cannot be simply shut off before the radiator is detached.

Figure 2: Now take a look at some of the damage a misunderstanding about radiator valves caused. First and second floors: tiles fall off after a good wetting of the backing plasters; middle floor: plasters are removed to aid the drying.

Figure 3: On the ground floor, what used to be a strip-floored reception room is now in a very sorry state. Little is left of the oak strip flooring, which suffered serious water damage from the floods above.

Figure 4: The leaks from the (TRV) central heating valve three floors above seemed to have caused the worst water damage to the bottom storey, where not only the strip flooring was ruined, humped up like a big dipper, but also plasters needed to be hacked off to help dry out the walls and ceiling linings which had peeled and blistered from the saturation had to be removed.