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Old 04-15-2010, 11:21 PM   #1
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Need to run gas line to Tankless Water Heater.

I will be installing a Rinnai R94Lsi tankless water heater to supply my two bathrooms on the second story. The water heater will be placed in the attic directly above the two bathrooms which share a wall. Obviously I need to run a new gas line to this location so I was hoping to bounce some thoughts off you all to get some advice.

I've sketched out my gas lines to make this easier:

The total BTU consumption is 456K BTU including the new Tankless which is 199K BTUs.

The longest run to any appliance would be that to the new Tankless which is 70 feet from the meter. So looking at the pipe sizing charts on the net, I need a 1 1/4" line from the meter. As you can see, my trunk line is 1 1/4" so I think that is good so far.

The new tankless water heater location is 30' from the end of the 1" line marked G. My original idea was to replace line G with a 1 1/4" line and then run a 30' 1" line from there to the tankless.

But after looking at this, I think I have another option. I could replace the first 14' of line E with 1" and then tee off it with another 1" to line H and connect the furnance to this branch. Then I could leave line G as 1" and simply continue the 1" line another 30' to my tankless.

Am I making any sense with either of these options? If so, which makes the most sense?
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Old 04-16-2010, 05:59 AM   #2
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You don't say where you are, I assume the climate will allow water lines in the attic??? Most localities do not like homeowners running gas lines. And this needs to be inspected whether done by a pro or yourself, so check local code.
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Old 04-16-2010, 02:56 PM   #3
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The Nat. Fuel gas code will give you the proper sizing but generally they frown on non licensed people running gas lines.
Always ask to see your contractors license!
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