close all gas valves before opening line?


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Old 10-18-06, 02:59 PM
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close all gas valves before opening line?

Planning to extend a run of gas pipe to accommodate new location of the dryer. I’m well versed on the fittings, pipe dope, etc. The other gas lines in my home go to the oven, furnace and water heater.

To do this work I will need to turn off the main. Do I also need to close the isolation valves at the oven, furnace and water heater? When I turn the gas back on I can bleed out the line at the dryer…what about the other lines? I’ve done this in the past (I’ve seen it done I should say) without turning the isolation valves off, and the only drawback was that the furnace took about 20 minutes to kick on, until all the air was purged out of the line. I know that air in gas lines is not a good thing….hence this question.

The furnace is in the attic, and getting up there requires removal of almost everything in the closet….but if this is a safety issue then I will of course do it.

Thanks !
 
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Old 10-18-06, 03:14 PM
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Just as a thought..... the very first thing I do when adding piping to existing piping is to install a new ball valve at the junction of the old work/new work. That way I can turn the gas back on quickly and not worry about the possibility of the problems you mention - nor the possibility of being without appliances in the event something goes wrong during the installation process.....
 
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Old 10-18-06, 03:21 PM
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Not really possible in this case. All I will be doing is removing a 3 foot piece of pipe and installing a 6 foot piece of pipe. And the piping will be drywalled (I checked with my local building inspector and this is permitted).
 
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Old 10-18-06, 08:07 PM
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There is no need to shutoff each appliance because air will get into the line before their shutoffs and you will have to bleed out each individual appliance when you’re done.
 
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Old 10-18-06, 09:01 PM
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ok, so the question now is can I just let the furnace run until it sees gas and kicks on, or do I actually have to go bleed the line?

The issue is access and moving everything out of the closet. Safety is the first priority of course. Thanks.
 
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Old 10-18-06, 09:43 PM
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If it has a standing pilot light you'll have to hold down the pilot button until the air clears out of the system. If it is a newer self lighting model then it should eventually light itself.
 
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Old 10-18-06, 10:38 PM
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the furnace is 2 years old and lights automatically. Is there any safety issues doing it this way? I would assume not, since when any gas powered machine is connected for the first time all the air must be forced out of it anyway by the gas pressure.

Just want to make sure. Thanks again.
 
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Old 10-19-06, 08:44 AM
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There are no safety issues. The furnace might shutdown if it doesn't detect flame after so long. That's a safety device to keep it from dumping gas everywhere. It should wait 5, 10 or 30 minutes and try to relight itself. If it is power vented it'll keep trying to light itself until it detects flame.
 
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Old 10-19-06, 12:04 PM
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great. Thanks !
 
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Old 10-19-06, 10:11 PM
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project complete

turned off the gas, installed the new piping, turned the gas back on and checked for leaks using soapy water. Nada.

Re-lit the pilot on the hot water heater, and the gas oven AND furnace fired up right away..no delay. Bled the line out at the new valve may have got most of the air out.

Thanks all !
 
 

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