Flexible gas appliance connector

Looking for an opinion on the use of a flexible gas appliance connector used to supply a furnace. My memory tells me this is not allowed but wanted to check. From the shut off valve to the furnace has to be hard pipe? Lack of sleep not helping my brain…


If you ask ten inspectors that question, you may get 12 or 13 opinions. Here’s the current IFGC 2012

Some local AHJ’s take a more conservative approach, but the IFGC allows it if protected. Check with your local codes to be sure.

In CA, all furnaces and water heaters are connected with flexible appliance connectors. Perfectly acceptable as long as they are installed per building codes and manufacturers installation instructions.

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John make sure the flex is one section with no connectors and that the flex does not go through the knockout.

No picture so assume you are not talking csst.

No it is not CSST. Here’s a pic. One thing I did not check (thanks Bob!) was if it entered the knockout of the furnace…

John call it out for location and entry that may cause mechanical damage (under the Unit ) ? what the heck ?..that’s ridiculous.

Also if more picture shots check for dirt leg,plus whats up with the condensate line ?..sorry off topic.

Condensate drains out the other side. This is a water sensor for the drip pan. Thanks Bob

Bob, you mean a picture like this? Just found this one, flex line entering knock out of furnace… underneath the furnace. Horizontal install in an attic. Go figure. The second pic is the hooks supporting the furnace screwed into the rafters, they are all bent and pulling out. An all around great install, not!

Yep the vibration can cut the flex.
Also like the vent at the powerfan.Hope its not the rangehood…instant fire.Even ignoring the mold created from a bath fan the plastic may get caught up in the thing…

I agree with the others.

Even where flex line is acceptable, that installation is not. Call it out.

Great pictures, John, especially why flex shouldn’t pass through the knock out, as Bob indicated. :slight_smile:

I regularly find the protective grommets either inside the front cover or my favorite, installed on the other side of the cabinet in the un-used knockouts! :roll:

John, I meant to get this to you before for your records or reference material. Grayslake currently uses the 2009 IRC which is identical to the IFGC.

Does not apply here Cam other than about protection which I have never seen at the knockout.
Maybe just me but Damn codes are boring to read and take 1,000 words to say what we all said in one sentence.
That’s why I like the forum so you guys can interpret for me into simple language.

In not sure what you are referring to when you say it doesn’t apply. It applies directly to John’s op.

Our opinions don’t determine if something is allowed. With protection at the knockout, it is allowed.

Question for the group - "Can anyone please provide a code that either allows or does not allow CSST to be used on a roof?



How do you mean “used on a roof”? Do you have pictures? We don’t know your location and it may make a difference.

Many energy companies state that it needs to be protected from mechanical damage and corrosive environments e.g. Flexible gas piping OK for exterior? post # 21 from 11 years ago.

This is from Duke energy:

5.14 Outdoors
When installed outdoors, CSST shall be protected from mechanical damage. A conduit or chase is required for installations in exposed unprotected areas within 6 feet of grade. Conduit shall be supported with proper size pipe hooks, pipe straps, bands, or hangers.
Protective coating must remain intact outdoors. Mechanical joints and associated exposed metal tubing shall be wrapped or protected by shrink sleeves. Appropriate measures must be taken to shield CSST from corrosive environments such as exposure to acid or chloride based cleaning solutions for brick or masonry.
Where passing through an outside wall, CSST shall be protected. CSST must be sleeved where passing though.

Ray Horn,
Next time you will get more and more accurate responses if you start your own thread and, fill out your profile. It is up to "Control Panel”, in the blue stripe, at the top of this page. Click on it.

Your answer will be found in the manufacturer’s design and installation guide, not too far from where they list the supports for roof mounting csst.

Please don’t resurrect old threads to ask a new question. Leave the zombies in the ground. Start a new thread.

Here are some installation instructions:
CSST Installation Instructions - Flexible Gas Piping, How To Install

Here you go, see page 42, keep in mind codes are always local.


Every intallation manual I’ve ever seen shows hard pipe comimg out of furnace. Usually “code” says to follow manufacturers instructions. Look at #6 in Camerin Andersons post.