A stopcock regulates water flow through pipes. A stopcock operates manually by turning a knob or handle. They can become leaky, stuck or otherwise damaged. They may also simply become seized, making them difficult or impossible to turn. This usually means it is time to replace the stopcock. A homeowner can have a plumber replace the stopcock, but he can also do the task without professional help. Only a few tools and supplies are usually necessary for this job. Stopcocks that are soldered in place instead of screwed into place have to be cut out with a saw or torch. This job may be best left to professionals or very capable do-it-yourselfers.
Turn of the entire home water supply. If you cannot locate the whole-house stopcock or shutoff valve, contact your local water company.
Open a tap in the basement or lowest story of the home. Also the tap most directly connected to the stopcock. This will relive water pressure.
Unscrew both stopcock nuts with a pipe spanner or other adjustable spanner. Completely remove the nuts.
Remove the olives, or small compression sleeves from the pipes feeding the stopcock. You may have to cut them with a hacksaw.
Put new olives on the pipes if the old ones have been cut, if not, reinstall the old olives. Place the stopcock nuts around the pipes that attach to the stop cock.
Apply pipe sealant around the olives and stopcock nuts.
Position the new stopcock in its installation location. Make sure it faces the right way. It should have an arrow on the boy indicating the direction that water flows.
Tighten the stopcock nuts with an adjustable spanner. You may have to also hold the stopcock straight with pliers.
Turn the main water supply on and check the stopcock for leaks.