Black Pipe Natural Gas Drip Leg Question

[rao]

At loooooooong last, I am installing a heater in my garage. It is a Cozy Direct Vent Counterflow DVCF403B-H http://www.grainger.com/Grainger/items/1PKY9

I have the furnace mounted and the vent installed, last step is the gas line. I have located a gas line that I can tap into nearby on one of the interior walls of the garage.

The question that I have is that the gas inlet is 2 5/8" off of the floor. I don't see how I can install a drip leg with that little room. I was thinking that I would run the pipe close to the furnace at around 12-18", put in a proper drip leg and then run hard pipe or a flex line to a ****** that would clear the outside of the furnace enclosure.

Any help would be appreciated. Thanks!

 

[pipehack]

You could probably get away without one BUT I would do with what your idea. Put one as close as possible. I would hard pipe it though. Flexies are really only for dryers and ranges.

 

[rao]

Sounds good. I can do it all with hard pipe. I am trying to figure out a way to T into the line in the wall without using a union, but I don't think there is a way.

 

[6t7gto]

I believe the furnace should be 18" off the floor. (gasoline fumes)
Why not just raise the furnace up and give yourself more ground clearance?
david

 

[rao]

It is designed to be mounted on the floor; the instructions show the minimum clearance to the floor to be 0". It is a sealed burner unit so it has air intake and exhaust from the outside.

 

[rickairmedic]

I would hard pipe it to the furnace and put your 6" drip leg next to the furnace . Also you will have to use a union where you T the line off of the existing line.


Rick

 

[rao]

Thanks. I found some reverse threaded ******* at McMaster but that might be more trouble than it is worth.

 

[kbs2244]

Sealed burner or not, if it is in a garage the flame has to be at least 18 inchs off the floor.
The zero clearance is for in the home installs only.

 

[russlaferrera]

What do you have against using a union?

 

[ozzirt]

Does the gas line in the wall continue to other outlets fitted with a drip leg?

I'm no gas fitter, but when we consider that a drip leg is merely a trap for debris, I would merely install my Tee junction upwards to stop debris from entering it and allow it to be swept down the main line to the next drip leg where it would be trapped. The new connection it could be elbowed out through the internal wall.

Having said that, I reiterate, "I am not a qualified gas fitter" and only have an engineering point of view of the problem.

 

[pipehack]

No unions in the wall. bad idea. plus against code.

 

[rao]

That's why I wanted to avoid a union. Since I need one I will have to keep the union and the rest of the piping outside of the walls, which is not a big deal.

 

[fireguy]

Sealed burner or not, if it is in a garage the flame has to be at least 18 inchs off the floor.
The zero clearance is for in the home installs only.

Ever see what happens when gas fumes hit an open flame? Do the 18", there is a reason for that part of the code.

 

[nate379]

Agree with it being on a stand.

I don't have a drip leg on my line to the boiler. Didn't even know about it until a few weeks ago. (I didn't install the boiler though).

How important it is? I could just turn the gas off and add one.

 

[redsky49]

The drip leg, also known as a dirt leg, is there to protect the gas train and burner orifices from gas born water and dirt. In a clean piping system, with best quality gas supply, there will never be a need for this. In the real world most systems develop some moisture from condensation, as well as some dirt or other contamination. Typically the drip leg is 6" deep, though there is no hard and fast rule. In a crappy system you could go 12" or more to avoid having to service the drip leg.

Some gas-fired systems, especially the recent energy efficient ones, are more finicky about gas quality, and gas quality varies between supplier, geographic location (altitude) and delivery piping quality. Additionally, the heating value for natural gas can vary from 900 to 1200 btu/cub. ft. Water vapor, hydrogen sulfide, etc. is removed from the raw natural gas by the supplier prior to distribution, but invariably the gas quality degrades over the transmission network. Your gas supplier can provide more information if you are interested.

The key is to provide this "trap" at the bottom of the vertical pipe nearest to the appliance. This makes it more likely (in theory) that you will capture small particles and moisture prior to the gas-fired device. Most codes show the presence of this device at the hook-up for any gas appliance.

This is mostly in response to Nate379's question. Hope this helps.

As always, offered only as opinion.

 

[porschedude996TT]

When I put the 3/4" gas line (50') for my shop build a few weeks ago, I cleaned it before hand with Lacquer thinner, a Wad of Green Scotch Bright on the end of a wire, and there was a bunch of trash that came out of the new pipe. Locally most people/contractors don’t put these drip legs in houses. I guess our distribution system and the gas is pretty clean and dry. I plan on putting one in since it only cost a Buck or Two for a Tee, a Cap, and a ******.

 

[nate379]

Are you supposed to clean that drip leg out every few years type thing or??

 

[porschedude996TT]

Are you supposed to clean that drip leg out every few years type thing or??

It would depend on the amount of moisture the gas company has in the gas and what condenses out. As for bits of dirt and scale from the pipe, I would imagain that a 1/2" x 2" or larger trap would give you years of life.

 

[nate379]

I'm going to try and put one. The only thing is the shutoff is more toward the boiler and the other shutoff is out on the meter. I was told if I turn off the one on the meter off it will close a diaphragm that has to be reset by the gas company.

 

[HoosierBuddy]

If you want to do it correctly, put in the drip leg.

That being said, the previous poster is correct. The drip leg will only work if it's the lowest section of piping in the house. In my old house, there were drip legs on the water heater and furnace, but they were above the piping in the crawl space. I had to take the piping apart in the crawl to add a tee for a gas fireplace. When I broke it loose at a union, I got showered with black liquid.

It was either cutting oil (doubtfully) or more likely just liquids that had settled out of the gas stream. I lived at the bottom of a hill and I think my gas meter was lower than most of the gas company's gas main, so my piping served as the drip leg for the whole neighborhood.

The comment on the BTU variation is interesting. I've never seen or heard of 1200 BTU per CF natural gas, but I've been on the receiving end of some 1100 BTU per CF gas. The only way that happens is if the price of natural gas has risen to the point that it is cost advantagous to NOT strip the liquids out at gas processing facilities. Normally they can sell those liquids for more than they can the natural gas on a BTU basis (gas is sold by heat content, not by volume). Anyway...the producers will stop stipping the liquids and just let them go into the gas stream. They raise the per CF charge for the gas because it's hotter. Then, the liquids settle out in the gas distribution system wrecking all kinds of hell with meters, regulators, and customer equipment, and everyone pays more for crappy gas...because the BTU content is sky high.

Crazy. The interstate pipelines are supposed to have dewpoint standards to prevent that sort of thing, but when gas gets scarce and the price gets high they seem to turn a blind eye to it. Next thing you know, I'm getting a face full of it in my crawlspace.

My current house has a basement and the furnace and water heater are lower than my service line so the drip legs should actually function. I've never seen anything in them though. I check them once every 10 years whether they need it or not.

BTW...I have no fricken idea what the "diaphram" the gas company told you about is. I do know a lot of gas companies don't want customers turning their own meters off and on because you can tear up a meter if you open the valve too fast. Besides that, turning a meter stop is a federally regulated pipeline safety activity covered under CFR192 and by administrative rule (The Operator Qualification Rule), you are supposed to be trained and "qualified" before you undertake the task.

But that's way too much information.

Phil