Help: Filling 85G tub with a 50G hot water heater

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@ngeLCD

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First of all, let me apologize for being that guy that joins and immediately starts asking a question with my first post. I've been a long time lurker, but just got a new house for which I need some advice. I did do some searching and couldnt find any posts with my specific issue, so here goes.

We had the builder install a 6' tub instead of a 5' tub in the master. Our old house had nearly the same water heater, a 50G Rheem (old house was Gas, new is LP), and it could fill the 5' tub well enough without running through the hot water tank. The hope was that the 6' isn't that much bigger and therefore we'd be ok. However, upon trying it for the first time last night, it didn't go so well. Before I spend a dollar, I'm going to crank the temp on the hot water heater and see if that fixes the problem. But, if that doesn't do the trick, I'm trying to figure out my options other than just replacing the water heater with a larger model. The tub isn't used too often, maybe 25 times a year, so I'd be happy with dealing with knowing after the tub is filled, we won't have too much hot water for a bit. The house has pex piping with individual runs to each fixture, so I have easy access to the tub water lines.

My immediate thought was to use a mini tank unit to provide more hot water. Or possibly a small point of use on demand electric heater to boost the temp of the hot water to the tub and to take over when the tank runs cool. As the current setup gets the tub close I'm hoping I can solve this with less than simply replacing the water heater.

Thanks in advance!
 

Terry

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If you crank up the water temperature, you should add a tempering valve and set it down on the output.
I do that so my mother can fill her deep tub. I set her's to 120 degrees. She's 97.
 

Reach4

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Is the water heater older? Is the water from a well? You might want to consider flushing the water heater. The thinking is that there could be a layer of material that is partially insulating the water from the heat.

Regarding filling the tub, remember that some water will be displaced when your mother climbs in. So maybe she could fill it a little less and still have water to the overflow once laying in the tub.
 

@ngeLCD

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Terry:
Thanks for that idea. At the moment its just me and my wife, but we do have a little one on the way, so it wont be long before we need to worry about a kid scalding themselves. I was unaware they made mixing valves for the hot water heater, so that seems like a great way to stretch a 50 gallon tank. That being said, is there any reason not to run the water heater at "very hot" the just have the mixing valve knock it back down to a safe temp? I know there will be a reduction in efficiency just due to larger delta between the water and ambient. Will running the water heater at max temp significantly effect the life of it?

The upside here though, as she's pregnant, she can only take warm baths for the time being. So I have some time to figure this all out. Haha

Reach4:
Its a brand new house and water heater on city water, and my wife is demaning her nice big tub work, haha. I'm hoping lifting the temp solves this...
 

Reach4

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Are you sure that the water starts plenty hot and the cools off as the tub fills? Is it possible that the water is not hot enough when filling the tub, even at the start?
 

Jadnashua

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The tank's life will likely be shortened some by running it hotter, but it is done all of the time. Where I live, ALL water heater installs are required to have two things: a vacuum breaker AND a tempering valve if they want to pass inspection.

Running the WH hotter makes it seem like a bigger tank. Depending on the time of the year and where you live, it could still be marginal. After a long cold spell where I live, I've measured my incoming cold water at 33-degrees F...nearly freezing. It doesn't take all that much to knock the temperature down, so you'll use more hot water than you would in say the middle of summer when the incoming water could be nearly room temperature (depends a lot on where you live and how the pipes are run).

There are a couple of WH tempering valve setups that are pretty simple to install as they're preconfigured, and just screw onto the hot and cold inputs, then the existing supplies are connected to it (this assumes you have flexible lines coming in/out). It gets a bit more involved if your tank is hard piped. Note, some places require flexible lines, some require rigid, and some don't care, so you need to know what your local code requires.
 

@ngeLCD

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I live in southeastern PA, so it doesn't get too cold for too long typically (if you ignore last year). Thanks for all the help. Trying a tempering valve is definitly what I'm going to try first.

Thanks
 
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