No cold water in shower

[Mr. Huevos]

Hi,

First time poster... Everything was working fine until yesterday, when the city shut off the water main on my street for a few hours. When it came back on, I was suddenly not getting cold water in one of the showers in my house. Everything else is working fine, including the sink in the same bathroom (hot & cold, pressure, no problems). This is in the upstairs bathroom. Hot works fine, it's just the cold. It's a single tap. All the way left (about 10:00) is full cold, all the way right (about 2:00) is full hot.

I've left it running on full cold, hoping it was just air in the pipes from the shut-off that needed to flow through, but after quite a while, all I got was a tiny trickle. I've read similar posts here that indicate it might be the pressure balancing valve, but I'm suspicious of a couple things: 1) it was working totally fine before the main shut-off occurred, and 2) this shower is used at least twice/day, so it's not like it should have been stuck from low usage.

I took apart what I could, but I'm not 100% sure what brand the valve is. It was in the house when I bought it. It may be Delta, but again, not sure, and I haven't seen any pics posted in the forums that look like it. So, here's a picture of it.



I like to think I'm handy (but ask my wife to be sure), and I can follow instructions (again...), but I'm certainly no plumber. I'm not sure where to go from here. I don't know how to check for a pressure-balancing valve, any kind of cartridge, or what that even would look like. There also doesn't seem to be any more obvious ways to take anything apart without breaking something. Is there anything I can do here myself before calling a pro?

Thanks very much.

[mtcummins]

Inside that cartridge, there is often a pressure balancing device. Basically what it does is if one input suddenly depressurizes, it softens the shock of the change for the person in the shower. This is a rudimentary explanation, but should suffice for our purposes here.

I had a valve (brand new) once that this device had gotten stuck to one side for some reason. I got the result you're having... only a tiny trickle from one temp or the other, can't remember which.

If you feel up to the task, you can take that valve cartridge apart a bit more, and find this balancer. You'll want to free it up, and make sure the lubrication on it is still there so that it can move freely. This should fix your problem. If not, the cartridge is probably $20-25, and you're done. I can't identify it from the picture, but I bet someone on here can.

The sudden decrease and increase of pressure on the lines could have caused this with the water mains being shut off/turned on. They also could have had a surge in the pressure or something while working.

[Mr. Huevos]

Thanks a lot for the reply. Any tips on disassembling the cartridge? It looks like maybe it twists, but I'm worried it's going to break if I shove any kind of tool in there. It's also hard to get any leverage, the way it's positioned. I've read about a special tool designed for this, but as far as I know, they are brand-specific and I'm not sure what I've got.

[mtcummins]

The cartridge is usually just slid into the valve body. There will be a ring around it that is threaded onto the brass valve body holding the cartridge in. I don't know what valve that is, and I can't tell too well from the picture if this is your setup, but most valves use some sort of system like that.

Once you have it out, I'd just replace it, to be honest. Its not enough money to fuss with it a lot, especially b/c it could be damaged in some way and you won't be able to fix it.

How to take it apart, no idea. I did mine just by figuring it out. But you will def want to get the cartridge out of the valve body first. And make sure the water supply lines are shut off before you do this

[jadnashua]

SOme cartridges have the pressure balance spool valve (or its equivalent) inside the cartridge, some use a separate valve. The cartridges generally are not designed to be taken apart. If it is a spool valve stuck, sometimes a whack with a mallet can restore things. I'd do that as a last resort, though. Don't bend the valve body!