Hi everyone!
I'm at a loss with this one. I have hot water coming out of the bathtub tap when the Moen valve is set to the hot position. However, when I try to use the shower, the hot water coming out of the shower is almost the same temperature as on the full cold setting on the Moen valve. I installed a new Moen valve about 1 year ago and the shower has worked perfectly till one week ago. Why wouldn't the hot water coming out of the bathtub tap be hot when the shower is used? (I don't think it's the valve)

Doug MacGregor

labman

This is definitely one Tom will have to solve. You might let him know if this is the standard set up where you shut the water off to the tub spout and then it goes up to the shower then. Also, do you have a standard hot water tank where the incoming cold water pushes the hot water out at nearly the same pressure?

speedball1

Sorry Doug, But it can't be any thing else but the valve.
Sounds like you might have a Moen valve with a faulty temperature balancing spool.
This spool has a balancing piston that controls the hot and cold water balance. It is actuated by pressure diffential and by diverting to the shower you are creating a pressure diffential. To replace the spool shut off the water and remove the knob and the face plate. The balancing spool is located right above the cartridge in the valve body and it unscrews. Just take it in and have it replaced. Mystery solved??

Doug MacGregor

Yes it's a standard set-up. I pull the knob up that is on top of the tap and the shower turns on. I am in a condo-apartment. There is a hot water pipe with a Tee connection coming into the bathroom. This connects to the basin hot water tap and the Moen valve at the bathtub. The water is hot at the basin and the bathroom tap but not at the shower head.

Doug

Doug MacGregor

I had to do a little research regarding your answer. The valve I have is a cartridge that has a balancing spool at the back of it. I should be able to remove the spool, clean it if necessary and reinstall it in the cartridge according to the Moen literature I found on their site.
A project for tomorrow.

Doug

Doug MacGregor

Well...tomorrow has arrived and I have discovered a few things.
1st...I pulled out the Moen valve. If there is a balancing spool with a cap on this it doesn't look anything like the diagram I have. I'm tending to think if Moen makes these without balancing spools then I have one of those because I cannot find it. Of course I'm not a plumber so maybe I'm not looking at this correctly.

2nd...I took the opportunity to flush out the pipes, and I noticed the hot water is about half the pressure of the cold water. Speaking to building maintenance, I've learned the water system in the building is being worked on.
I've also noticed a hot water pressure drop in the kitchen due to this work.

3rd...I reduced the cold water pressure coming into the bathroom which works, but if I do that there isn't enough water pressure to stop the toilet from running after a flush.

So...I guess I have two choices. Wait until the work is finished (which could be a while as the entire building is being re-piped), or replaced the single valve type with separate Hot and Cold valves.

Doug

speedball1

Hey Doug,
The problem is not in the valve itself so replacing it with another valve isn't going to help. Tough it out untill they quit disturbing pipes and sending crud throughout the system. Then you can began to clean out the inlet ports of the various cartridges and the aerator screens. You,indeed, have a standard Moen Tub and Shower valve without the balancing spool. but that could have been your problem, the symptoms are the same. Regards, Tom