DIY How To

Draining Hot Water Taps

Hot water can be generated and supplied to the taps using a number of different systems. There are water boilers that are installed solely for the generation of hot water on demand, some homes use a combination boiler to supply the hot water to the taps as well as heat the home and some homes will have a hot water cylinder used to store hot water, the cylinder is usually located in an airing cupboard.

Drain hot water taps


Vented Hot Water Cylinder (explanation)

To drain the hot water taps and associated pipework, close the valve on the cold feed to the hot water cylinder and turn on the hot taps. It may seem unusual to close the cold feed to the hot water cylinder, but the hot water cylinder uses the pressure of the water in the head tank, to force the hot water from the cylinder. Thus if you remove the pressure you stop the hot water coming out. Remember that even when the water stops flowing from the hot taps, the hot water cylinder will still be full of water.
If you can't find a valve on the cold feed line to the hot water cylinder, you can tie up the float valve on the cold water head tank as shown and drain the head tank by opening the hot taps.

TipIf you can't isolate the cold feed to the cylinder and want to save the hot water in the cylinder, drain the head tank by turning on the cold taps. This will only work on an indirect cold water system.

 
Unvented Hot Water Cylinder (explanation)

To drain the hot water taps and associated pipework, you must isolate the cold water feed to the cylinder, this can be done by closing the main stopcock on the rising main, where it enters your property or by closing a stopcock local to the cylinder if one has been fitted and turning on the hot taps. It may seem unusual to close either stopcock, but the hot water cylinder uses the mains pressure feeding the tank, to force the hot water from the cylinder. Thus if you remove the pressure you stop the hot water coming out. Remember that even when the water stops flowing from the hot taps, the hot water cylinder will still be full of water.

 
Combination Boiler

To drain the hot water taps and associated pipework, close the valve on the hot water outlet pipe as it leaves the combi or close the stopcock on the cold water feed supplying the combi and turn on the hot water taps.

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