Random lack of hot water in shower


Old 01-15-18, 04:58 PM
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Random lack of hot water in shower

For the life of me I cannot figure out why we occasionally have a lack of hot water in the shower. Sometimes it happens at 7 pm when the kids are showing, sometimes it's at 11 pm when I'm showering. No laundry, no dishwasher, nothing...

We have a hot water heater in the basement, which I'm told isn't that old, though isn't that new.

For the most part things are fine, but often enough the hot water is iffy...

Happens in summer and winter. In the winter, maybe has to do with the heat (we have baseboard heat), and the hot water running the baseboards? Though I don't think so as sometimes heat is on and shower is fine, other times it's off and shower is cold. Doesn't seem to fit any patterns. Happens in both showers.

And sometimes it actually seems better (hotter) when lots of showers have taken place (i.e. rather than running out of hot water after a while, it seems to be able to keep up and keep making hot water). Maybe when it hasn't been used in a while (i.e. the first shower of the evening or one late at night), it's not as 'ready' and has let the temp drop a bit in the hot water heater?

Thanks for any thoughts!
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Old 01-16-18, 04:36 AM
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Do you know if the temperature is dropping at the hot water heater or is it delivering consistently hot water and something in the house is reducing the temperature?
You could tape the bulb of a digital thermometer to the line at the HW tank to check this.

A thing that sometimes causes a problem is a Y connector on something like a laundry sink with both the hot and cold water on at the same time and the flow stopped by a valve.
The cold water can bypass the hot with cold water being delivered when a hot tap is opened downstream.
A common occurrence in my workplace.
Old 01-16-18, 06:46 AM
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I'm not sure where the temp is dropping but will try and test it as you've suggested.

Just last night, my wife and 1 child were out, and I was home with the other child. Literally every 2 minutes I was called in as the water was too hot, then too cold, then too hot... And it really was. It would get cold, so I was turn the lever towards hot, 2 minutes later it was way too hot so I'd turn it back towards cold...

That's a bit of an extreme example, as normally it's simply a lack of hot water, but in this instance it was hot cold.

And again, it doesn't make sense (to me anyway) that it would do this for the first shower, or a shower late a night (when nothing else is on or has been using hot water in a while). Or maybe that's the problem, maybe my tank for some reason 'works' better when it's used a lot, and if it's been sitting for a while it's lost temp and can't keep up?

I occasionally find myself at 11 PM turning the lever all the way up as the hot water keeps declining. But at 6 or 7 when one kid after another showers (and sometimes for a long time), the hot water is just fine the whole time.
Old 01-16-18, 02:58 PM
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Is it just in that particular shower or all over the house in other fixtures also'

Just in that shower the problem could possibly in a defective tub/shower valve and not in your boiler at all, especially fluctuating that fast it sounds like a direct problem with the mixing part of the valve sticking.

Just a thought.
Old 01-16-18, 05:17 PM
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Just to add food for thought. You have a storage tank connected to the boiler. The boiler heats the water which then is transferred to the tank. On a call for house heating..... the boiler temperature rises. When the call ends... the boiler returns to a previous lower temperature. You could let us know what temperatures you are seeing on the boiler gauge when there is a problem.

Ultimately a few pictures of the boiler, storage tank and associated piping could be very helpful.
Old 01-17-18, 02:05 AM
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Just in that shower the problem could possibly in a defective tub/shower
My thought also, a bad cartridge that controls scalding could be bad and flipping from one extreme to the other!

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