We are having some trouble with the hot water in our home. Sometimes we get hot water out of a faucet, sometimes it's cold. Sometimes our master bedroom shower is hot, but the upstairs shower won't get hot. I had a hot shower in the master bedroom this morning but just 5 minutes before, my wife couldn't get hot water in the kitchen at all. This is leading me to believe it might be a bum mixing valve above my water heater, but I'm hoping for a second opinion! Thanks, Mike

Edit: to clarify, in case it's different elsewhere, I live in Ontario Canada. Homes here are required to have hot water regulated to no hotter than 49C (120F). The home we're in has a single master thermostat mixing valve above our water heater to regulate hot water temp to the whole house. I'm assuming that because we *do* have hot water, just not reliably (sometimes the tap will be hot, then cold for a minute, then hot again, that this is where the issue is... but I'm green to plumbing in general.



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mike, is the mixing valve adjustable ? have you tried twisting the knob when the water is running cold? just as a test to see if it works again even temporarily. most replacement elements for those valves are not very expensive and are pretty simple to change.

1st verify the integrity of your temperature mixing valve to be sure it is truly blending the waters and the strainers and not filled with debris.

Also, make sure that your temp mixing valve is rated for the amount of hot water being used at the same time. A properly sized temperature mixing valve is most important.

Best Wishes

If you have a mixing valve on your water heater and a thermostatic mixer on your shower... that could be an issue too.

Best Wishes

There are several possibilities but since some depend on how the piping is installed, there is no point in referring to them unless they apply to your situation. Call a local plumber to diagnose the problem and see if there is a cure for it.

Thanks, everyone, for the answers so far. Sorry for the delay responding, was out of town on a business trip - should've planned the post of this question a bit better!

To update:

1. Unfortunately, twisting the knob doesn't do much, it's already set to a good temp as well, though adjusting it didn't fix the issue

2. Simultaneous water usage doesn't appear to be the cause, as the issue can occur with a single faucet, even if the tank is full and no water had been used for hours prior.

3. Though I used the shower as an example, it happens with other faucets as well, particularly in the kitchen.

After a bit more testing, I find that I *always* have instant hot water using the sink in the basement next to my water tank. Also, as soon as I turn that hot water tap on there, I have hot water right away at the kitchen faucet that previously was only cold.

Does this indicate some sort of pressure issue? Something that's causing the taps upstairs to not pull hot water through the mixing valve, where the high pressure tap downstairs right next to the tank triggers it? Sorry if my terminology sucks - again, very green to plumbing in general. Happy to get a plumber in here to take a look, just thought I'd see if I could rule out something really simple that I could potentially fix myself.