TPR valve exit on a point of use heater


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Old 10-16-13, 02:32 PM
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TPR valve exit on a point of use heater

I will be installing a tiny 2.5 gallon point of use heater under the kitchen sink to get hot water quicker from the tankless that is far away.

Reading the reviews on the Bosch point of use heaters, several people said that they hooked up the TPR valve to the sink drain (with an extra mini-P trap, or before the sink P).

I thought by code the TPR is supposed to exit above the floor or above a pan?

I like the idea of taking the TPR to the drain. If the exit is just hanging in the air, if the TPR fails it would mess up the cabinets. Also I think a pan is a joke as a solution, as it would just overflow.

How would you hook it up to protect the cabinets, but also to be somewhat code compliant for a tiny little heater?
 
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Old 11-25-13, 06:35 PM
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Bumping this for some insight from the knowledgeable folks, I have the same questions. Maybe I'm over thinking this but I'd also like a better solution for a tank failure than a small pan, but the pan is below my sink drain. Tempted to route the spigot of the pan through the cabinet and floor into the basement, I'd rather have it drain down there than in a finished kitchen.
 
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Old 11-26-13, 05:53 AM
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Why not exit the TPR through the wall to the atmosphere with an elbow outside? Feasible?
 
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Old 11-26-13, 08:29 AM
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I may go this route, a bit unsightly outside but it seems like the most professional solution. I'll need to rig it up so the pan also drains the same way.
 
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Old 11-26-13, 10:07 AM
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I think the idea of a pan is that most failures end up in slow drips from the TPR valve. Either the valve itself starts failing or the temperature rises a bit too much and you get a little release. The pan will catch the drips and you'll be likely to notice it.

I think it's quite rare for the TPR valve to fully release and release a lot of water. I'm sure it has happened, but you're probably way more likely to have a pipe break, washer hose fail, etc. I'd also be more concerned about a blockage backing up to the sink and overflowing the standpipe you use for the TP overflow.
 
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Old 11-26-13, 10:31 AM
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Thanks for the input. My primary reason for a pan was to address any tank failures, having learned this the hard way with our primary tank in the basement a few years ago. Any pan is going to be so small it won't help against a significant leak unless it has a drain; I'm liking the idea of feeding it through the wall to dump outside.
 
 

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