View Full Version : Gas LIne Sizing?

10-19-2009, 08:49 PM
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.



Doherty Plumbing
10-19-2009, 11:40 PM
Not meaning to sound rude but your question is impossible to answer without the BTU of the dryer you bought and also the pressure your gasline is running at.

I would assume it's low pressure, or 7" W.C or less. If it is then I'm gonna just guess that you'll be putting a strain on the system. I'm too lazy this time of night to size out the gas line for you (especially without knowing the input of the dryer and pressure the line is under.).

If you're running a 2psi system then I'd be willing to bet that you're perfectly A-OK.

We still need more info :D

10-20-2009, 12:38 AM
Thanks for the response. I will get more info.


10-20-2009, 01:09 AM
The dryer manual says that gas requirements for the dryer are 10 -13 WC. I could not find a btu rating. I also found on my gas meter the tag read 5 psi. Are these the right places to be looking for this information? Should I hook up a pressure gauge to the gas meter to know exactly the pressure in the system?

Peter Griffin
10-20-2009, 02:53 AM
5 psi is the maximum pressure rating of the meter, not what the incoming pressure is necessarily. The National Fuel Gas code book has all the charts that you will you need once you know the incoming pressure and the dryer input.

10-20-2009, 08:42 AM
YOUR system would NEVER be a 5psi system, nor would it be a 2psi system because it does not have the demand and parameters which would make a 2psi system logical. Given your numbers, you are already undersized. You should have 1 1/4" from the meter to the range, and 1" from there to the water heater. 1/2" is all you need from the main to the dryer.

10-20-2009, 09:55 AM
I talked with the gas company and they informed me that my system was a
7" WC or 1/4 lb system pressure. They also informed me to size the line to my dryer using a 35,000 btu rating.



10-20-2009, 01:50 PM
I went to a house party in Girdwood last year.

Jamie's band played for it.

Here's Jamie's band playing at Blues Central (http://www.youtube.com/watch?v=7JI915fhVNg)

And Arize playing at Blues Central (http://www.youtube.com/watch?v=lYGRQTmLP7w)

I would love to get back there and do some fishing and check out the skiing.
It was a good time, good food and my first taste of "road kill" moose.

10-20-2009, 03:43 PM
Glad to hear you had a great time in Girdwood. You should definatly make it up for some skiing.


Peter Griffin
10-20-2009, 04:30 PM
[QUOTE=AK_Nick;227671]I talked with the gas company and they informed me that my system was a
7" WC or 1/4 lb system pressure. They also informed me to size the line to my dryer using a 35,000 btu rating.

Well, there's a couple more pieces to the puzzle so with manual in hand you should be all set.

10-21-2009, 06:12 AM
That is the pressure I used from my calculation, and also the same dryer btu, since both are standard specifications.