In order to carry out any work on the water system in your house, you will need to empty the pipework first. It may not be necessary to drain down the whole system, but at least the required section will need to be drained.
Locate and label stopcocks and valves
So that you are not caught out in an emergency, it would be as well to identify and familiarise yourself with the location and effects of all the valves and stopcocks in the house. Should you have an emergency, you will be able to quickly switch off the supply or isolate a particular section.
It can be useful to label the various controls.
In an emergency, time saved can also save damage.
Draining cold water
Taps supplied directly from the mains can be isolated simply by switching off the stopcock on the rising main. This is often located under the sink. Open the tap to release the excess water.
Draining the tank in the attic
Indirect fed items are served by water from the cistern in the attic. The water from this may be stopped by closing the valve from the cistern to the section you are concerned with. Alternatively, supply from the cistern can be stopped totally.
To do this, place a length of wood over the tank and tie the ball valve up to it in the closed position. The tank can now be emptied by opening all the cold taps supplied from it.
Switching off the rising main
The same effect can be achieved by switching off the rising main and opening the cold taps. This removes the necessity to tie up the ball valve but has the downside of also cutting off supply to the direct-fed parts of the system as well.
Draining hot water – vented cylinder systems
Before working on the hot water pipes, switch off the boiler and immersion heater.
Close the cold supply from the storage cistern in the attic to the hot water cylinder. It seems odd to do this, but it is really quite logical. The cold supply to the cylinder is what forces the hot water out of it when you open the taps. So by turning off the driving force, you also turn off the hot water.
If there isn’t a valve for the cold supply or you can’t identify it, follow the instructions earlier for emptying the cold water cistern in the attic and open the cold taps. The effect will then be the same, as no water is available to drive the hot water from the cylinder.
Emptying the WC cistern
This can be done using the same process as for the cistern in the attic. Remove the lid of the cistern and tie up the ball valve using a length of wood across the top.
Some WCs have an isolating valve in the pipework just before the cistern, which can be closed instead.
Once the supply has been stopped, the water in the cistern itself can be removed by flushing the WC.
Emptying the cold storage cistern
Switch off the rising main or tie up the ball valve.
Open the taps supplied by this cistern to remove the water.
This will empty the tank down to the level of the outlet pipe.
If the latter is not an option (the taps can’t be opened for some reason) or to remove the water below the outlet level, use a bucket to empty it, or drain it out by syphoning with a length of hosepipe routed from the bottom of the cistern to the nearest bath.
Emptying the hot water cylinder – vented type
Turn off the boiler and immersion heater and close the cold feed as described earlier.
Switch off the power supply to the immersion.
Open the hot taps to release water.
At the base of the cylinder, there will be a drain cock. Attach a length of hose to this with the aid of a jubilee clip if necessary. Run the hosepipe to an outside drain or sink/bath/WC at a lower level.
Open the drain cock and the water will be released from the cylinder.
On some systems, there is also a coiled pipe full of water within the cylinder. To drain this, switch off the electrical supply for the heating system, and close the supply of water to the expansion tank. This is a small cistern located in the attic (usually) which supplies additional water to the heating system when required. It also allows excess water caused by expansion to be released.
Drain the water from this coiled pipe using the cock located for this on the boiler.
If you are not able to identify this for certain, you should consult a professional plumber.