A water heater should have a shut-off valve on its cold water inlet. so you need to locate your unit’s water heater and shut of the hot water while you work on the hot water valve to the washer. If for some reason your water heater was not installed with its own cold water supply shut-off, you’ll need to turn of the the main supply valve (and at that time install a shut-off to the water heater).
I totally agree with “nicktheplumber” that if your water heater is not installed with cold water supply, then you need to turn off the main the supply valve. If you are still facing problems, its the right time to call professionals.
If your home heating system should break down or stop working properly, you should consider professionals to get it repaired. I would like to share that in order to have your heating system repaired properly, you should contact only reputable contractors.briancooper2013-03-07 15:32:58