SHOWER HOT WATER SCALDING

There is an anti scald in most showers. There is a ring just under the handle that you can choose the position you want the handle to turn to. Someone must have under guessed the hot setting for that shower when putting it together, or they just didn't know. There is also another type that is a pressure balance to prevent scalding when a toilet is flushed etc. if that is the case there is no adjustment. It has to do with the way the house was plumbed.

probably have a kink on how water line feeding valve..if possible to cut drywall bhind tub valve and inspect pipe at bottom plate...moen faucets are equipped w/ anti scald device, pressure balanced (newer models) and this could cause cold water to overwhelm hot water...

Hi,
No it more then likely is because of fluctuating pressures...this could be because of other water usage in the house or even in the water entering the house...to see hwat it is the water pressure would need to be monitored at different locations to find the source of the problem...likely if it happens when somewhen else in the house flushes a toilet then you know where it is...

heatman101

The Delta shower has a rotational limit stop designed so that when another fixture is activated, such as a toilet or dishwaser, the water does not go to extreme hot or cold. The reason for this is that the Delta shower unit is not pressure balanced or does not contain an anti scald device. The pdf document below will show how to adjust the water tempature if you feel it is too cold. Please use caution as it is probably set the way it is to prevent scalding.

http://www.deltafaucet.com/media/Product_Tech_Docs/Maint_Installation/50001to80000/51975RevH_4.15_15e05.pdf

Your Moen valve is equiped with an anti-scald device (as part of the valve cartridge) which prevents someone from getting scalded by hot water if there's a sudden demand for cold water, i.e. a toilet flush, washing machine filling, etc. Fortunately Moen stands behind their products and will provide a new cartridge.
Contact Moen and describe your problem.

This is a common problem with this type of shower mixer valve. They are not very good at regulating with pressure change. Your options are somewhat limited to not flushing the toilet or using any other taps when in use, repalce the mixer valve for a modern ceramic unit or installing a 2 vane hot & cold shower pump.

If it is a two handle tub valve, then more likely no. But if you want to be sure, get into shower, a nice hot one and then have someone flush the toilet you will find out real quick.

This is typical for an installation without a balanced valve/anti-scald valve on the shower.

If you are using manual on/off valves on the shower, about the only way to fix this is to install the device mentioned in the previous paragraph.

I had a customer a few weeks ago that had the same problem. When the water heater was installed they crossed the supply lines. They had the inlet as the outlet. Esentially, the water heater was plumbed in backwards. Also there could be a miss piping somewhere in the house but it would probably be near impossible to find it right now without tearing up foundations. Also check that the faucet is not plumbed backwards as well. Especially if this is a single handle faucet that you are referring to.

You need to check the age of your water heater. If it is pretty old, it can be sloughing off debris that can get caught in the hot side of the faucet. You will need to turn the water off to the unit, remove the guts. While someone is turning the water on slowely, flush out the the valve. Take a flashlight and check for debris that is caught. I have spent a few hours digging out debris from water heaters before. After you have done this and your still not getting water, check the scald gaurd for the right temp. Typically these don't just "jump" out of adjustment on their own because they have a small retaining washer that holds them in place. I doubt it is the scald guard if everything was working just fine before. Plus, the bath faucet has the most flow than any other faucet in the house so this will be the first place that debris will usually travel. Good luck