Shutting off the water at the main stopcock will stop the water from coming into the storage tank. It will not top hot or cold water that is already in the tank from getting to the appliances such as the bath or the sink. It will take some time for the reservoir to be drained. Turing off the water to the tank will be easy if the washer needs to be replaced or other parts of the system need to be fixed. If this water cannot be turned off the tank will need to be drained.
Depending on how old the water system is, the valves along the pipe work may or may not be able to be worked on.
Old plumbing systems more than likely do not have the isolation valves.
Modern plumbing units may have a valve that is near the cold and the hot water tanks.
The newest systems will have a service valve near the outlets.
The gate valves are usually close to the cold water tank, or they are near the outlet in hot want tanks. It may pass through a room of the ceiling if they are not easy to find. It is pipework has been boxed in it may be around some screws. To turn these valves off turn them clockwise.
These valves are found on most modern plumbing systems. To turn them off use a screwdriver and turn them a quart of the way. This valve will then open, and when they are at a right angle, they are closed.
There is a Difference in Valves
“Gate valves are often considered to be unreliable by high industry standards” said Dave from cgis.ca. “Even if they are fully closed, they may still allow some water to get through. They often need to be replaced if there is a problem with the plumbing system.” Do not put a stopcock into the gravity feed system. They need a specific amount of water pressure. This will not give the gravity system enough pressure to operate entirely.
If the valve cannot be located along the pipe run, then the system will need additional work. It is best to turn off the water supply that leads to the tank. The outlets will then need to be opened up. All of the water will need to be drained before proceeding. With an open water tank, it may be helpful to block the outlet by inserting a cork into the outlet pipe.
If the system is not properly drained, they a quarter turn service valve should be put in the outlet from the tank. This will help avoid future issues. When working on an older plumbing system, there are some things to keep in mind. A service valve that is 15mm will be able to fit on a copper pipe that is half an inch. To get a 22mm valve to fit onto a ¾ inch pipe, the process will not be as straightforward. Additional working will need to be done to make sure that everything is fitting correctly.