Physically impossible problem!

[Huyt]

I am beaten. Here are the facts:
My NJ home had an extra bathroom added before I bought it. In this bathroom are twin basins and a tub/shower. All of the fixtures are made up of two faucets and a spout, so no mixer valves.
When we bought the house the shower was fine. Then it started intermittently running cold on people when other faucets still produced hot water.
Since then the problem has become permanent.
Right now the water from that shower/tub comes out at 100 degrees with just the hot faucet open. The water from the hot basin faucets in that same room produce hot water at 130 degrees.
I assume that somehow, somewhere cold water is entering the pipe supplying hot water to that bath. I have turned off the water to the kitchen mixer tap. No help. In the master bathroom I have done the same to the mixer taps in the basins. No help. I have turned the master shower mixer to fully cold, but can't find a way of actually isolating that valve.
Is there a way I could isolate that mixer by taking off the face plate?
BUT I assume that the new bathroom shower/bath and basins are all supplied by the same line. So if cold water is reaching the hot-water pipe to the bath why is the hot water in the basins not affected?
All the hot water comes from one gas-powered unit in the basement.
Only that one tub/shower is affected.
Should I be calling an exorcist?
Cheers
Huyt

 

[phishfood]

I believe that it has been a LONG time since tub/shower valves that aren't pressure balanced have been legal to install. Can you post a picture of your valve?

Regarding the basins not being affected, the tub valve usually pulls much more water than does the lavatory faucet, so it will usually show a cross over problem before a sink faucet will.

 

[Huyt]

Dear Phish
Here's the shower.
What other possible causes of crossover problems are there?
Thanks
Huyt

 

[SHR]

All of the fixtures are made up of two faucets and a spout, so no mixer valves.

Right now the water from that shower/tub comes out at 100 degrees with just the hot faucet open. The water from the hot basin faucets in that same room produce hot water at 130 degrees.

Ahh, the mixing valve is right there on the shower wall in your picture. It seems you have a very common, easy to solve issue. Remove the mixing/pressure balancing cartridge from behind the faucet handle on the right (I think it should be bottom) in the picture. Bring the cartridge to your plumbing supply store and match it up to a new cartridge. If you can identify the brand, you should be able to order one free from your manufacturer. Replace the cartridge and I bet your problem will be solved.

 

[wood4d]

the shower valve has a temperature limiter under the handle which is removed with an allen wrench. After removing the handle the adjustment is very fast to do. The other valve looks like an on/off for the handshower.

 

[Huyt]

OK, I have isolated (turned off both hot and cold supply) the washing machine, mixer faucets in both master bathroom lavatories and the master shower, the kitchen mixer faucet, the third bedroom mixer shower and the laundry mixer faucet. There are no more places with mixers. All the rest are separate spigots for hot and cold water.
The problem shower/bath (which is not a mixer valve) still maxes at about 112 degrees, but the lavatory faucet next to it reaches 150 degrees.
Is there any safety valve or other such item that could be installed out of sight and which could cause this cross-over problem?
Thanks again
Huyt

 

[SHR]

Ahh, the mixing valve is right there on the shower wall in your picture. It seems you have a very common, easy to solve issue. Remove the mixing/pressure balancing cartridge from behind the faucet handle on the right (I think it should be bottom) in the picture. Bring the cartridge to your plumbing supply store and match it up to a new cartridge. If you can identify the brand, you should be able to order one free from your manufacturer. Replace the cartridge and I bet your problem will be solved.

the shower valve has a temperature limiter under the handle which is removed with an allen wrench. After removing the handle the adjustment is very fast to do. The other valve looks like an on/off for the handshower.

You have been given the answers to your query. It seems you have done a lot of messing with your faucets but you do not mention trying the solutions you were provided.

 

[Huyt]

I believe that have indeed done what was asked. The photo was of the master bath shower. I isolated that one (mercifully it had little shut-off screws by the valve). The shower that runs cool is not a mixer valve. So I can't change that cartridge.
Or have I misunderstood something?

 

[journeyman]

You have to remove the handle and pull out the cartridge and install a new one that is what shr is referring to

 

[Zanne]

http://homeguides.sfgate.com/replacing-shower-faucet-cartridge-57457.html

You can google how to replace shower lever cartridge and there are many videos to show you how to remove the lever.

Those are interesting tiles with the little symbols on them. Its neat.

 

[Huyt]

First, thanks all for your help.
The shower that runs cold does not have a cartridge. It has two separate spigots that feed a spout which can be diverted to the shower head.
The below-temperature water comes when I turn on just the hot water spigot at that bath/shower (forgive any terminology errors, I was born in England). So I don't understand how cold water supply to that bath/shower could be crossing over - unless there is some hidden valve designed so keep the water at a safely low temperature. To look more closely at the plumbing there I would have to remove drywall.
I am kinda hoping you'll tell me I have missed the point and that there is a cartridge even in a two-spigot set-up.
Thanks
Huyt

 

[johnjh2o]

I may be missing something but the picture you posted is a mixing valve with a cartridge.

 

[journeyman]

The handle with the big ring or escution is the on the cartridge is in. Remove handle and then remove cartridge. Install a new cartridge and reinstall handle. Trust everyone here there is a cartridge

 

[Zanne]

Check this out: http://toolmonger.com/2009/12/01/how-to-replace-a-shower-faucet-cartridge/

You do not need to remove drywall. You just need to remove the lever to access the cartridge.

Keep in mind that it doesn't matter if you have a knob like this or if you have a lever like the one in the photograph. That part is just for looks. The insides are basically the same.

In this one you can see that the person chose to remove the escutcheon. I don't know if it was in the way or if they just wanted to avoid scratching it.

Levers need cartridges to work. The cartridges are what control the flow of water. In the off position they block the passageways so no water can flow through. In the on position they allow the water to pass through. Sometimes they get worn down and don't block or they get gunked up and don't let water through. In those instances they need to be replaced or cleaned.

 

[leojr]

The shower that runs cold does not have a cartridge.

If I'm following all of this correctly, the worn/old cartridge is cross flowing cold water into the hot pipe and when the cooled warm water gets to your single handle faucet, well, it's cooler.

 

[Mr_David]

Fixed the photo.
I suggest removing the handle, and cover plate from the valve in the picture. Post another photo. This will help Identify the make.
Some times you have to pull the cartridge out to Identify it.
That looks like a mixing valve to me as well.
Some pressure balance valves have floating spool inside the cartridge that often gets stuck, restricting the flow of hot or cold water.

 

[Zanne]

I know this is off-topic, but were those tiles with the symbols already there when you moved in or did you have those put there? They are very neat and I'm trying to figure out if they signify anything specific or if they were just random things that someone liked. The snail-like ones sort of remind me of some Thai numbers.