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Two hot water pipes for a sink?

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dschae1

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After the rough in on my daughter's new home, we noticed one of the sinks in the Master Bath has an extra hot water line plumbed in. The two on the left have red PEX pipe under the insulation. The one on the right is white PEX pipe for cold.

So, anybody know why there are two hots?

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Mitchell-DIY-Guy

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I bet it’s a return line for recirculation. Had the same in my home built new in 1992. Nice to see copper and insulation installed.

if the master bathroom is on the 2nd floor and water heater in the basement then it will work nicely without a pump. Lived with that arrangement for 27 years and it worked flawlessly...👍👍👍
 

HWSleuth

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Do the stub-outs on left side tee together or are there two separate drops? Is there a 1/2” stub-out at the water heater not connected? Sounds like what was previously suggested, a return loop. Good suggestion about second floor and making it possible to be a gravity return not requiring a pump!
 

dschae1

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Thanks for all the replies!
Some answers: First floor, no basement, two separate lines, no tee, the toilet is on the other side of the bathroom with a cold water line plumbed.
There is no water heater yet as this is just the rough-in phase. There are two pipes (a red and a white) that are just looped back together (second picture), probably for the pressure testing. It will be a wall mounted tankless unit in the garage.

I too was thinking recirculation, I guess I need to take a ladder over and trace the line, see where it goes.
BTW: the end pieces are Copper, it is Pex for most of the lines everywhere else. Seems to be how they do it these days. Here's a picture of some lines before insulation.
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TomFOhio

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Why don't you just ask the plumber what the second hot water line is for. He is right there and can
explain it to you.
 

dschae1

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Why don't you just ask the plumber what the second hot water line is for. He is right there and can
explain it to you.
Would love to...but this is new construction about 25 miles away. We get to drive over after work some evenings and see what was done. The trades are gone by the time I get there. I should be able to trace the line this weekend though.
 

Jeff Handy

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Just leave a nice note for the plumber or general contractor taped to the wall somewhere they will see it.
With your cell number, asking about the two hot stubs, and admiring all their good work so far.
Maybe they will have a minute to call you, maybe not.
 

dschae1

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The answer I got back from the builder:
Will be for a mixing valve for the master bath tub. Code requires that you cannot fill that master bath tub with straight hot water. That mixing valve will mix a little cold water with the hot at that master tub to prevent it from being filled with 120 degree water and someone falling in it etc. Only required at the master tubs. At our trim once tops and tiles are installed the plumbers will install the valve when they set sink faucets etc.
 

dschae1

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That’s a cool way of doing things. Here we have to temper the water right at the water heater
It is a logical idea, however, there is another bathtub in the home and it does not get this feature. I guess the plumbing code only requires it for the master? Only the master bath. Wouldn't the kids bath be a better choice for something like this?

Update to earlier posts...I traced the line and it is a direct run to the master tub. Up the wall, over the ceiling and down to the hot on the tub!
 

dschae1

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Bonus: I found the code for this:

424.5 Bathtub and Whirlpool Bathtub Valves
The hot water supplied to bathtubs and whirlpool bathtubs shall be limited to a maximum temperature of 120°F (49°C) by a water-temperature limiting device that conforms to ASSE 1070 or CSA B125.3, except where such protection is otherwise provided by a combination tub/shower valve in accordance with Section 424.3.
 

dschae1

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In other words your master tub must have a roman tub faucet. Your other tub must have a single handle
faucet.
You know, that does make sense. I bet a single handle tub cannot deliver full hot water, there is always a little cold mixed in...right?
...And yes, the master tub will have a roman tub faucet,
this one
in fact. But I do not know which of the rough-in valves they will choose.
 

TomFOhio

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The single handle faucets can be set to a lower temp. The two handle roman faucet can't unless you use
a mixing valve like they are going to do.
 
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