My shower is leaking horribly and I need to replace the cartridge assembly in my water valve. As I understand it, I need to cut off the water so it doesn't gush all over the place when I remove the cartridge. I have found the hot water cut off switch on the hot water heater. When I turn it off, the hot water turns off and none of the sinks or tubs in my place runs water when set to hot.

But the cold water still flows freely. I am under the impression that I need to cut off both kinds of water in order to avoid a deluge when I remove the cartridge. Is this correct? I can't find a master water cutoff valve of any sort for my individual unit.  You'd think each unit would have a master cutoff switch.. I wonder if I'm confused about the need to cut off both kinds of water.

You need to cut off the water main where the water enters your home.  Look for where the feed pipe comes into the basement.  There is usually a valve and a pressure regulator at that location.  If you cannot find it, look for the water meter outside, in my case this is covered by a small manhole cover near the street, and shut off the water from there.

Quoted: You need to cut off the water main where the water enters your home.  Look for where the feed pipe comes into the basement.  There is usually a valve and a pressure regulator at that location.  If you cannot find it, look for the water meter outside, in my case this is covered by a small manhole cover near the street, and shut off the water from there.

Thanks. It looks as if I might have to do that. I thought there might be individual cut-offs for each unit in the building, but this seems to be an incorrect assumption on my part.

Quoted: Quoted: You need to cut off the water main where the water enters your home.  Look for where the feed pipe comes into the basement.  There is usually a valve and a pressure regulator at that location.  If you cannot find it, look for the water meter outside, in my case this is covered by a small manhole cover near the street, and shut off the water from there. Thanks. It looks as if I might have to do that. I thought there might be individual cut-offs for each unit in the building, but this seems to be an incorrect assumption on my part.

I don't about where you're at, but here in So. Calif, there is a shut-off valve on the main coming from the into the house. There are no individual angle-valves(shut-off) like in the bathroom wash basin for the showers.

You definitely need to shut off ALL water. You'll either have to find a main valve for your individual unit or shut off water to the entire building. Once the main valve is closed, you won't have to worry about turning off the hot water one, either.

I just replaced the cartridges in a couple of Moen shower valves. It's pretty easy, so if need be the time that water would have to be turned off for the entire complex would be minimal.