With plumbing, as with many DIY situations, the golden rules, are:
BE SAFE, and BE IN CONTROL
The first one is mostly common sense, in terms of working well away from any electrical wiring, if there might be some water leakage. If you HAVE to work close to any electrical wiring, or supply point, make sure you can isolate it by throwing the appropriate circuit breaker. Also, don’t forget that in Bathroom plumbing, any earth bonding clamps must be replaced, if rerouting pipework. For radiators, don’t be tempted to put the wire and clamp under the floor. Regulations state they MUST BE VISIBLE. Obviously this does not apply to the ones on the bath frame.
BEING IN CONTROL: for plumbing, this really means knowing where the valves are to isolate YOUR part of the system you are working on, and ensuring they are operative. Just turning off the water at the mains supply in the kitchen IS NOT ENOUGH. The cold water loft tank can hold up to 100 GALLONS, The hot water tank 30 to 50 gallons, and the central heating header tank plus radiators can be around 20 to 40 gallons, depending on the number of radiators.SO, ensure you know WHERE THE SHUT-OFF TAPS/VALVES ARE FOR THESE, AND ENSURE THEY ARE WORKING. They are USUALLY in the airing cupboard, and there is sometimes a shut-off (service valve) where the cold water “rising main” goes into the large loft tank. The airing cupboard ones are usually the “gate-valve” type, with red hand-wheels. There should be 2 on the inlet and outlet of the CENTRAL HEATING PUMP, don’t touch those, unless you are changing it.If draining the central heating system, you MUST turn you boiler off, and the timer controls to off positions, to ensure that the boiler will not try to fire up while the system is empty. Otherwise, although there ARE safety overtemperature sensors, you MIGHT damage the heat exchanger. NEVER ATTEMPT TO MAINTAIN OR CHANGE ANYTHING RELATED TO THE GAS SUPPLY OR GAS VALVE, OTHER THAN TURNING OFF THE GAS FOR SAFETY REASONS. ONLY CORGI REGISTERED TRADESMEN CAN REPLACE OR MAINTAIN THESE.
If you have to turn the water off completely at the main supply or loft tank to replace something, like a tap, or a cistern, think about including a SERVICE VALVE at an appropriate place that is easy to reach. They are quite cheap.