Weird hot water problem

Greg_S_H · 04-19-2008, 07:47 PM

There was an electrical storm the other day, and I guess I took a hit because my hot water heater was knocked offline and the electronics were all fried. I got a new one, and now I have a strange problem.

I've got a single knob control for hot and cold water, and I've traditionally been able to shower with the indicator pointing straight up, maybe moving it to the left a little if the water started to run cold. Now, I get that same performance in the tub's water spout, but when I engage the shower (a pull-up device), the straight up position is cold water. I have to turn the knob all the way to the left, and the best I'm able to get is tepid. But, as I said, if I turn off the shower and just use the spigot, all the way to the left is scalding hot. And, I get the full range between middle and full left.

What could be the cause of this? I mean, there's not much to a shower--the rod just diverts the water from the spigot to the shower head. How can there be a temperature difference? The only thing I can think of is that the cold water valve is stuck open, but why does it only affect the shower?

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Dennis Nicholls · 04-19-2008, 08:09 PM

When the plumber installed the new water heater, he must have dislodged a chunk of crud which is now lodged somewhere around the diverter valve.

What kind of pipe do you have? Rusty galvanized?

Greg_S_H · 04-19-2008, 08:33 PM

I think it's copper. The house is about 33 years old and that hasn't been touched. I don't even have access to the pipes unless I take out a bunch of tile. I may have to if it's the valve that's a problem.

If some crud was dislodged, will it work itself out, or will I probably have to get in there?

drobbins · 04-19-2008, 09:26 PM

I wish I could remember better, but ran into a similar issue helping a friend with a leaky shower control. It turns out there is a safety feature in the control if the pressure is different between the hot and cold side. This would prevent only hot water from coming out if the cold was turned off somewhere else. I thought it reset once the pressure equalized.

Greg_S_H · 04-20-2008, 01:09 AM

I bet there's something to that, Dave. I have some pressure problems. Sometimes when I turn off the faucet (it pushes inward to do so), the water continues to flow. I have to pull it out slightly to get it to stop. Also, when the sprinklers are running, either water comes out the faucet here, or the pipes shake until the faucet is turned on. I bet whatever is causing all of that just finally got worse to coincide with the new water heater.

Jeff Ulmer · 04-20-2008, 10:20 PM

The shower problem is a weird one, but crud would be my guess - the temperature equalizer should affect both the spigot and shower. You would have to open the valve I would think. As for the shaking, are you sure you don't have an airlock somewhere? I would open all the faucets in the house to make sure there is no air in the line, and also pull all the aerators so any crap in the pipes gets flushed.

Greg_S_H · 04-20-2008, 10:59 PM

After they put in the water heater, I turned on the kitchen sink and it ran fine at first and then dropped off. I just took your advice and removed the aerator. I didn't see anything, but the water blasted out when it was off, and it seems to be back to normal. With that in mind, do you think it would be a good idea to start by taking off the shower head and letting the water flow out the open pipe? Any other solution will require a plumber, because I just removed the cover and everything is welded back there. I wouldn't have room to work without removing tile even if I knew what I was doing.

Jeff Ulmer · 04-21-2008, 02:27 PM

I would certainly pull off the shower head in case anything is back there.

You should be able to get inside the tub valve from the front unless they screwed up the tile job - the control mechanisim should just screw in with the ball behind it. If you do end up taking this apart, be sure to plug the drain first, and be very careful when removing the valve stem, as there may be springs/washers inside that you don't want down the drain or falling into the wall cavity. Also, if you do end up disassembling the valve (which isn't a big deal, just be careful), unscrew it gently so you don't accidentally break a solder connection (they shouldn't break anyway, but will if they are marginal to begin with). If you know he make of the valve you may be able to find an exploded diagram which will show you what to expect inside.

Greg_S_H · 04-21-2008, 04:28 PM

I'm in the middle of this right now, but after I took the shower head off and blew water through the pipe, I looked in there and there was a big, fat rubber washer lodged near the end of the pipe! It isn't the shower head's washer, because that is still inside the shower head. I pulled it the washer out with some plyers and, while I don't know why this would be the case, my problem may well be solved. With the dial to the left, the water out of the pipe was really hot.

This washer is longer than it is wide and is about an inch long and a half an inch thick. It's got a really small hole in the center.

Edit: I won't be able to tell for sure until later, but I don't think my problem was fixed. I think the initial burst of hot water I felt was because hot water was already running through the pipes. It definitely cooled to tepid with the shower head back on. My guess is that the valve that is supposed to shut off the cold water isn't working, so I'm getting a mix. It may be an easy thing to disassemble the valve as you say, but I'm not sure what I'm looking at. I pull off the handle and there's a cylinder extending back to the pipe where the hot and cold water are connected. Maybe it's not welded like I fear, but I didn't want to mess with it last night. I may go to the store and look at their assemblies to get a better idea of what I can do.

Jeff Ulmer · 04-22-2008, 03:49 PM

That cylinder I'm assuming is chrome or whatever finish your valve is. It will unscrew from the brass body, or there may be a locking ring (unlikely). It sounds like one of the washers in the valve got pushed out of place, which could also be the cause of your banging problem, as when the faucets aren't sealed, they can vibrate.

Here's a video showing the disassembly, there are some other links from this page.

How To Repair a Tub-and-Shower Valve | eHow.com

I think your assessment is correct, but depending on the kind of diverter you have, there should be no difference in temperature between the spigot and shower head, as the diverter should be after the mixer.

Jay H · 04-22-2008, 06:45 PM

Here's a shot in the dark:

If it is a valve problem, I've replaced my valves in my shower faucet. However, I have a 2 faucet shower with separate hot/cold faucet taps so I have 2 valves in my system. But to replace them, it's fairly simple if you have the proper tool and slightly hard if you dont

What happened with mine is that the tabs on the valves shaved off or broke such that my hot water lever was overrotating instead of stopping. I'd be able to stop the hot water but not necessarily in the same clock position as before and if I kept turning, the hot water would turn on again. This lever is supposed to have positive stops when off and when full max which wasn't happeneing.

Once I took the handle off, there was a plastic lockring which you could remove with either a long nosed pin spanner. A spline tool you could buy from Moen, or slowly, via needlenose pliers. Being the cheap resourceful bastard I am, guess which method I got it off?

Anyway, once the lockring was off, the valve comes out and was replaced with a new one. Just for fun, I did the cold water valve too, because I'm not that cheap.

Maybe this helps you look at your valve but I found Moen has a pretty good cut out on their website but perhaps if you know your mfgr, check that.

Could it be possible that your valve might of had the same problem, the tabs that keep the valve fixed might have worn off, allowing the valve to rotate... making your diverter's temp setting off.

Jay

Greg_S_H · 04-28-2008, 08:12 PM

Thanks, guys. You put me on the right path, and now everything is squared away. My brand happened to be Moen, and their website was indeed awesome. They showed me that I had a cartridge and just needed their little tool to loosen and remove the cartridge. I believe the o-rings were the problem, but I just replaced the entire cartridge. The shower is now hot and the sprinklers can run without pipes shaking and water pouring into the tub.

It was a very easy process. I just had some concerns about breaking a pipe or something, since everything has been in place since the house was built, I believe. I probably would have tried to turn out the brass pipe attachment if I hadn't seen the cartridge demo at the Moen site. As it was, it was a bit of a challenge to get the cartridge out. I needed some Kroil and a good wrench. Fortunately, it came out without creating new problems.

Greg_S_H · 05-06-2008, 02:05 AM

In the week since I replaced my cylinder, I've discovered some things. To start, the cylinder was bad, and had been needing replacement for years. I'd have done it a lot earlier had I known how easy it was, but the new hot water heater forced my hand. I thought it was a coincidence that the cylinder finally gave up the day I got the heater, but that wasn't it at all. I have since discovered that the hot water pressure is lower than the cold. This is not just on this shower, it's any tap in the house. On mixed taps, it makes it difficult to get warm water. It's either cold or really hot. My question is, is this likely an installation error that can be fixed, or are the new water heaters regulated to put out lower pressure? Sort of like a low flow toilet or shower head?