I have a question about black iron gas pipe. I have done a fair amount of fitting these together and have heard "I catch three threads and I'm happy" to "I torgue them down until I can't do it any further with a 10" or 12" wrench" from plumbers and reading in forums. What do you do when you are fitting small nipples into a furnace? The area is too tight for wrenches and the nipples are small to being with.

I have tightened them hand tight and then put a small nipple on the elbow to turn it again and it starts to get pretty snug where I may not be able to make another full revolution without tools but no tools will fit. They can be moved when I attach the longer pipe to them if I don't back the inside up with a wrench while tightenting the outside. I used Pro Dope and usually tighten very tight and never have leaks. I plan to test with an electronic gas detector that is very sensitive but how likely is it for a leak developing down the road from vibration? Perhaps I should check them once a month for a while? I will be supporting the pipe external to the furnace so it shouldn't move but being a sealed furnace it seems a small leak would be dangerous as the gas can build up but should be expelled by the draft inducer before firing provided no sparks from the motor.

Just wondering how others have handled this type of situation as it must be common to have to come off a gas valve and turn 180 degrees back inside the small are to use the alternate side of the furnace for gas supply.

As you do NOT have the knowledge to install threaded pipe PROPERLY you should NOT be installing gas pipe at all !

ALL 1/8" through 2" NPT threads 'should' make up a total of 7, repeat 7, turns as that is the number of threads inside said fittings.

However, 5-6 turns is minimally acceptable. 3-4 by hand, 2-3 by wrench

Personally, I like Permatex #2 for gas work.

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

I agree from your post that you should Not be doing this type of work however if you insist some information for you is better than where you appear headed at least you asked
Pipe threads generally are" 3 turns by hand 3 with a wrench and leave 3 for inspector"

The black iron gas pipe should enter the cabinet case to the gas control box Do not run gas flex thru the cabinet due to vibration even if there is a gromet

The gas flex and shut off is all outside the furnace box and has a gas sediment trap which has to be installed for the gas to change 90 degrees and I personally check for gas leaks in a situation like this with kids bubble used at parties to blow bubbles

Don't screw around with gas if you are leanring as you can and may regret doing so

Thanks to both of you for your replies. I understand your hesitation in giving advice about gas and appreciate that you still replied.

A plumber once assisted me with repair of old leaky gas valves and unions in a 100 year old home. He taught me the basics but I have also researched proper methods and plumbing codes. I also learned quite a bit from my father. I have found many leaks in gas plumbing over the years and repaired them without incident. It is way too common to find natural gas leaks in the old style shut offs and unions in older homes. Many times when I removed these parts they are threaded only two or three threads deep and stuck together with hardened compound. I know the newer stuff from China may be different and it also depends on the age of the die used to cut the threads but when you seek advice about what is best, or what is good enough, there doesn't seem to be a standard for that and many times it comes down to opinion and experience. Some guys are shown something one way and it always works for them so thats what they do, or its the product that they always use even though there could be better, safer, and longer lasting ways to do things. I asked this question because this forum has proven to be valuable resource and while it seemed what I had was "good enough" I wanted to make sure I did it the best it could be. Liability is about who to blame when something goes wrong, I intend to make sure nothing goes wrong. Having as much information as possible from several resources helps me make sure there isn't something I missed or something I had not considered. I am not perfect but I do know more than many of the guys out there who wing it and don't consider all the angles or have a healthy respect for gas or whatever it is they are working on. I have heard from them too, and I know they aren't doing it right. Unfornately it is also too common to pay a pro and have to fix it later, at least in my area and at the prices I can afford to pay. I feel bad for the people who don't seek out the knowledge and are inadvertently taken advantage of by the guy who doesn't do it right but had all the best intentions but results in repairs perhaps years later when his work fails.

I properly sized the gas lines according to the chart and farthest appliance, verified it with the contractor who is doing my ductwork but also installs furnaces and extends gas lines. I used fittings that were legal by code in my area (no bushings), installed shutoffs where they should be and were none before, used ground union joints after the shut offs and closest to the appliances as I could get, installed 4" drip/debris legs under the tee at the bottom of the vertical drops under the tee that goes into the furnace/WH, hard piped everything with no flex lines, and used pipe dope only omitting it from the first few threads on the fittings closest to the appliance gas valves. I tightened everything tighter than it needed to be counting threads and viewing the inside of elbows and fittings as I assembled. I usually turn until I think I won't make it another revolution and still line up the fitting properly if I try to go farther. I have never split a fitting but since I use only a 10-12" pipe wrench (on 1/2" I doubt I have the strength to do that. After posting I found a way to remove some components from the furnace to get a wrench on the fittings and support the pipe as to not put stress on the valve or furance burner assembly. I was able to get one more revolution out of them and still be within the turns and visible threads that you both mentioned. I think I was looking for more experienced opinions about the minimum required so I would feel more confident that I had exceeded the minimum. The last thing I want to do is go too much and split the softer furnace valve assembly or have to dissasemble it all later. It is much easier to turn the fittings going into the valve than it is to turn them in the black iron fittings and I tried several street elbows to see if I could find a tighter one with no luck. I just about buried all the threads but maybe 1.5-2 and it just felt too easy compared to the usual fittings.

I find the bubble method to be a pain because it relies on visual inspection and proper application in tight and dark areas where it is hard to see all around the fittings. Because of my respect for the dangers involved in doing this kind of work I invested in an electronic explosive gas detection device. It is very sensitive and has detected leaks where bubbles did not. It allows me to test my work but also periodically inspect for leaks very easily without a mess and in a way that I feel confident that it will detect even the slightest leak. I don't know what your opinions are of these devices but it seems like a modest investment for anyone who works on gas regularly. I do not but I have three homes that have natural gas and have had leaks that I detected by nose alone and now I can check periodically to make sure those old pipes fittings are still holding. Those leaks were NOT in my work but from what I assume were professionals 30-40+ years ago. I maintain zero tolerance with leaks but I also know that there are many tiny leaks that exist for years undetected and do not cause any issues. Once again I do not accept them but they are common.

I didn't want to get too far in my assembly and have to take it all apart. I feel confident now that I have had the line pressurized and have tested for leaks several times.

Thanks again for your replies.

It appears you actually do good work ~ better than some 'pro work' I have encountered.

There ARE standards for National Pipe Tapered threads (formerly known as Iron Pipe Size).

ALL 1/8" through 2" female tapped threads are DESIGNED for 7 (seven) thread engagement.

ALL 1/8" through 2" male NPT threads are designed for engagement of 2/3 of their 'running length' ~ e.g. 1/2" & 3/4" (M)NPT = 14 tpi / 11 threads actually cut for 3/4" 'running length' / 7 threads engaged in fitting, leaving 4 exposed including the 2 imperfect 'starters'.

see:
[www.engineersedge.com]

[note: hand tight thread engagement = 5 threads]


It is sad to hear that you have only encountered the 'shoemaker' jobs, BUT, the good jobs are still leak free.

ps. the old style cocks were designed to be greased and periodically 'tightened'

pps. I would not settle for less than 5 thread engagement including 2 'power turns'

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 2 times.

Excellent information, I do appreciate your time.



Edited 1 times.

welcome

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

WHO has assembled these gas systems, because once they are put together, there is no reason they should EVER leak, vibration or not.

quote; I would not settle for less than 5 thread engagement including 2 'power turns'

Some day, I might actually COUNT the number of turns, but probably not since I have NEVER done it in the past 60+ years. If I were screwing a pipe into a fitting, I would have to make a mark on it and then count as it passes the "indexing" mark, WAY TO MUCH bother.



Edited 1 times.

MY do-do don't stink, MY joints don't leak ... EVER

I probably, however, take 5% longer to complete my work

OF COURSE I DO NOT COUNT TURNS ON EVERY JOINT

I just count a couple after setting / adjusting the dies

I check when doing REPAIRS, as improper thread(ing) causes many leaks

DOH

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

- READ THIS ARTICLE -

A gas engineer is a highly skilled expert who provides repair and replacement gas services. No repair of a gas problem should ever be attempted by someone who is not qualified. There are serious risks attached to this. As soon as you smell gas you should contact a gas engineer.

Fitting Carbon Monoxide Alarms
One sure way to detect a gas problem immediately is to get an alarm. An expert can help you select and install the proper audible and visual alarms that can keep your home or business safe. Carbon monoxide is extremely toxic and your engineer will be able to instruct you on risks and what you can do to reduce them.

Emergency Work
Leaks are treated as emergencies due to the toxic nature of gas and the fact that it can be explosive. Gas cookers, boilers, central heating systems at homes and business may operate on gas. You will want to make sure you call in emergency help as quickly as possible if you suspect there is a leak.

Appliance Testing
A certified expert can regularly inspect your heating systems, boilers, gas cooking appliances, radiator or hot water system. You need to know that each of these appliances works properly and routine maintenance is the only way to be absolutely certain.

Residential Pipework
Homes are often fed gas in the form of either Natural Gas or LPG (Liquified Petroleum Gas). These gases come in through pipes that run throughout and or beneath a house. Gas engineers are able to make sure your home complies with current safety regulations.

Advice:
If you suspect you have a gas leak of any kind you must call a qualified gas engineer immediately

You should have your home gas appliances serviced regularly by an expert.

Safety is absolutely paramount when dealing with gas so you must be certain to inspect the certification of your gas engineer to make sure they are qualified for the job.


Thanks!