Gas Line Sizing?


Old 10-19-09, 08:36 PM
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Gas Line Sizing?

I am installing a new gas line to convert my electric dryer to a gas dryer. I have done gas line work before and understand the processes and risks. I just need help to make sure that I am supplying enough gas to my appliances. I am going to try and explain my system as best as possible.

Starting at the meter I have a 1" main that supplies all my appliances. 14.5' from the main I have a tee that I will use for my dryer. 5 additional feet I have stubbed a line for my range. 6 additional feet I have a line stubbed to my furnace. At this point my main ends and is reduced to a 3/4" line to my instant hot water heater.

The run to the range/oven is 20.5' @ 1/2"
The run to the furnace is 3.5' @ 3/4", then 2' @ 1/2"
The run to the instant hot water heater is 21.75' @ 3/4"

The pipe in question is the new one to my Dryer this will be 28 feet at either 1/2" or 3/4"? This is where I need help.

My furnace has an input rating of 66,000 - 45,000 BTU/hr
My instant hot water has an input rating of 180,000 max - 15,000 min. BTU/hr.
I am not sure about the range/oven, but it is a standard four burner range and oven.
The gas dryer I just bought is a standard 7.0 cubic foot dryer. I am not sure the BTUs.

Sorry for the long message, but I have noticed from previous listings that more info is always needed.


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Old 10-20-09, 12:17 PM
Join Date: Nov 2007
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I'm not a plumber. I have well-head gas here in West Virginia. My main runs part way along the back exterior of my house. There are 3 drops into the house. Two at each end of my garage and the last into the crawl-space.

Each drop into the garage is 1/2" black iron pipe. At the garage door end is a space heater. Run length is less than 3'. At the house end is a gas dryer and the water heater. Run length is less than 10'.

Dryer............... 22,000 BTU/Hr
Water Heater.... 32,000 BTU/Hr

You might try the library for the International Residential Code book. But I'm not sure how helpful it would be.

Old 10-20-09, 01:01 PM
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Question Gas Pipe Size

To figure gas pipe sizes you have to start from the whole load on the system, without those measurments you are just guessing. You have to get the btu rating for the stove and the dryer, I would also double check the furnace rating; seems low to me.
Old 10-22-09, 01:40 PM
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If you have narrowed it down to 3/4" or 1/2" then if I were you I'd just run 3/4" and be done with it. There is no worry of running to big of a line that I'm aware of so rather than risk sub-par performance pay the few additional bucks and run 3/4" to the flex connection at the end.
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