Water Meter – The Water Meter, which you can usually find in your basement or just outside your home, will have a shutoff valve attached directly to it. Usually there will be two shutoff valves – one on each side of the meter (supply and home). To effectively shut off your water supply, turn the valve located before the meter.
Toilet Supply – Sometimes you do not need to cut off the main water supply to your entire house. It can be disruptive and the people in your home may not appreciate not having drinking water or a shower while you are working on the plumbing. So, when working on the toilet, always look for the toilet water valve located behind the tank. Sometimes this valve will be on the floor – other times it will be located on the wall just behind the tank.
Finding Wily Supplies – Sometimes the water supply may not be located where you would expect. It might be behind appliances or access panels or above your head somewhere. Most of the time, the water supply will still be in the basement, so start there and look carefully for the root of the pipes. Since most of the pipes in your home will originate at the supply line, you can usually trace them back to a single source.
If you still cannot find your main water supply line and shutoff valve, that does not mean it is hidden in the floor somewhere or outside. Sometimes, the supply lines are just in odd places, either because of strange construction or poor renovations by a past owner. If this is the case, get a second pair of eyes to help you hunt or as a last ditch option, call a plumber who will be able to more easily follow the lines back to their source. Nine times out of ten, you should be able to find and handle a main water supply on your own. But never rule out calling for a professional’s help if things get more complicated than anticipated.