View Full Version : Can I hook the flexible gas line directly into the heater?

12-04-2007, 04:00 PM
or do I have to have a black pipe line going into the heater unit and hook the flex line onto that? THanks.

12-04-2007, 06:03 PM
Most likely - Yes

But I would check with your local building codes to make sure.

I called our local inspector and verified that I could use flexible pipe to hook gas up to the furnace.

12-04-2007, 07:10 PM
I don't understand your question, but generally what I see these days on basically all installations is black pipe coming to within a couple of feet of a furnace/heaters gas valve ending at a tee with a capped nipple facing down (for a drip) and a shut off valve mounted above the tee. The appliance connector runs from the outlet of the shutoff valve to the load.

It might actually be better to mount the valve upstream of the drip...but I've seen it both ways.

I was always pretty old school on my piping, cutting and threading pipe and using a single union to connect the black pipe to the gas valve...right up until my favorite HVAC guy ridiculed me for wasting so much time. His opinion was that if we were supposed to run black pipe all the way to the load, God wouldn't have invented appliance connectors. Dunno. Since then I switched and started doing my stuff his way. It is definitely faster and IMHO unions are more likely to leak than an appliance connector.

Not really related, but in trailer parks, they have to use flexible connectors between the trailer and the gas meter. I got into a big argument with an inspector on the logic behind that and he finally retreated to "it's not my job to defend the wisdom of the's my job to enforce the rules."

I heard that. Good Luck!

BTW...don't ever run an appliance connector through a wall. It ain't allowed.


12-04-2007, 08:20 PM
Flex apliance connectors are nothing more than an invitation to a disaster.

Either pipe it in black iron or pipe it with the PVC/ss flex gasline.

12-05-2007, 09:27 AM
or do I have to have a black pipe line going into the heater unit and hook the flex line onto that? THanks.

Scott, your point is that the gas valve is located within the furnace cabinet. My inspector said that rigid black pipe needed to extend form the gas valve out to the exterior of the cabinet at which point you could attached the flexible gas line.

12-05-2007, 06:19 PM
You must use black iron from the gas valve to the outside of the furnace this is code nationwide once you are outside the furnace install a T fitting on the bottom of the T put a 6 " nipple and a cap on the top of the T put a small nipple and a shutoff above that from there you can use flex.


12-05-2007, 10:52 PM
Thanks guys, I probably didn't ask the question very clearly. I have a black iron pipe coming to within about 5 ft. on my heater. It has the shutoff valve, a T, a 6 in nipple and then a cap at the bottom. I was wondering if I can then take my flex pipe and run it from the T straight into the heater? It sounds like the answer is yes. The only problem I might have is the 5 ft. distance from the T to the heater might be too long for the flex line I have. I will either have to try and find a longer flex line that will go the whole distance or run a 2 or 3 ft. pipe from the T to get me closer to the unit so I can then use the shorter flex line. I hope all that makes sense. Let me know if you think there might be a problem with that. Thanks.

12-06-2007, 09:24 AM
I think Rick hit the nail on the head. You aren't supposed to run a flex line through the steel side of the heater. Sometimes that means you need to install a long steel nipple in the gas valve to bring your connection point outside the heater.

You should probably try to get closer than 5', as most appliance connectors are shorter than that. A lot of hardware stores will cut and thread pipe for you, if you can take them the measurements. Don't forget to use pipe dope on your NPT threads.

You've got pipe wrenches right?


12-06-2007, 09:59 AM
Thanks Phill ( see Hoosiers and Kentuckians can get along LOL ) yes that was what I was saying the Flex line CANNOT PENETRATE THE FURNACE CABINET and yes home depot as well as lowes and I am sure menards will cut black iron for you although it also comes in lengths from 1 foot to 5 feet at most box stores plus nipples from a close nipple up to 12 inches you also need to make sure the gas line is secure and tripple check all connections either with a leak detector solution or soap and water mix.I will also say use pipe dope on every connection do not use teflon tape use pipe dope ( and plenty of it ) it is easier to wipe off excess when your done than have to redo the joint becouse its not sealed.


12-06-2007, 10:13 AM
Either pipe it in black iron or pipe it with the PVC/ss flex gasline.

Just be careful with the PVC/ss flex selection. Very recently, this method is coming under increased scrutiny in this area. A good friend of mine was recently found 'not at fault' for a home fire a year ago that was caused by the failure of one of these gas lines. He is a qualified gas contractor and he is meticulous with his work. This particular failure was linked to the manufacturer which was a well known supply company within the industry.

Be careful!