Is a gas union allowed inside the furnace cabinet?
I know of nothing that would prohibit it.
The union was leaking and I just wanted to make sure that it is allowed in the cabinet.
Another question pertaining to unions. There was no union on the water heater line. (Or none that I could see) There is supposed to be one correct?
With a flex line there would be no purpose for a union.
By the way. I do not see a dirt leg or a shut off valve for the DHW. I see a valve for the stub out only.
What the general consensus with drip “dirt” legs? Do you recommend them on any furnace/water heater where they are not present regardless of age? Do you recommend them on newer ones in which they should have one based on current code but do not? Basically, do you recommend retrofits?
I don’t recommend them at all, because our utility company does not require them. . .
maybe not due to moisture in the gas but what about the sediment that can develop in the line over time? Also, what if you have a unit that has the “install drip leg” label and one is not installed?
If I saw such a label, I would certainly recommend installing one. I have never seen such a label. . .
Don’t know about you guys, but I prefer hard pipe.
to use the right techniques for flare fittings.
http://www.contractorssolutions.com/Information/images_Water-Heaters/Drip-leg.jpg
http://www.contractorssolutions.com/Information/images_Water-Heaters/Assemble.jpg
http://www.contractorssolutions.com/Information/images_Water-Heaters/Use_flare-fitting.jpg
Flared fitting with flex hose might be alright, but when it is kinked like in the picture, it make me wonder if it is right.
Marcel 
Hi to all,
David, nothing to do with the piping issue, but I would suspect a heat exchanger problem based on the corrosion just to the left of that burner bar
Regards
Gerry
Unions or bushings in concealed locations are prohibited according to my Code Check. Personally, I wouldn’t get too bend out of shape over it if it’s tight. However, unions tend to leak more often than threaded couplings.
That is correct but the furnace cabinet with excess door is not considered as a concealed area.
This very true I find more leaks on unions than most anyother fittings but try to change a gas valve with a coupling in place of a union and you will be using a sawsall. I have observed that to many fitters will use a union to compensate for a misaligned pipe and just pull the two ends together with the union which most useally leads to a leak.
I could stand corrected but I think the drip leg is left over from whem they used to manufacture gas from coal ,hence the name coal gas.
http://www.zetatalk.com/energy/tengy112.htm
They used to cooke the coal and coal gas had a lot of moisture in it the left over from the manufacture was coke and this was sold to people to heat their homes,
We used it when I was a kid last century and it was alot cheaper then coal not as much heat.
… Cookie
Drip legs are required on all black iron gas supply lines in Massachusetts. I hardly ever find a drip leg on flex piping though. I call them out on black iron piping only.
I agree with Gerry on the furnace. There’s signs of flames shooting out of the burner area. This issue may have been corrected already, but it still needs to be noted.
Usually when I find these signs, I shut the unit down and watch it fire up. Then write up my results.
Flexible appliance connectors are the preferred method in this state. When I see a complete “hard-pipe,” I will always recommend upgrading. . .
In preference to this mess Jeff. ha. ha.
http://www.nachi.org/forum/attachment.php?attachmentid=14216&d=1188588585
I do like gas flex lines that look like this.
That makes me feel better. ha. ha.
Marcel:) 
Just to throw a twist into this thread would a drip leg be required on a gas Pac or as some describe (package unit) in States or areas that require a drip leg???
Charlie;
What the hell is a gas Pac? ha. ha.
Never to old to learn and this peaks my curiousity.
If I had to guess, I would say yes, just before the final connection of whatever it is.
Marcel 
Jeff, why do you concider flex lines as an upgrade to hard-pipe? I can certianlly understand why it is a preferred method as they are quick to install but why chance a system from hard-pipe to flex if the hard-pipe is already in place?