Resize Gas Lines

Tom M

Can anyone tell me how you handle adding an additional gas line. If you wanted to add a gas grill or interior fireplace would you need to resize the branches and feeders of the whole supply line or take new supply from an infrequently used source.

Ron The Plumber

Sizing Gas lines is sized by total btu's

Your plumbing / mechanical code book should have a flow chart to say what size the lines need to be.

JamesNLA

Well....kinda sorta, but not really.

What are you adding? The BTU's that you are adding to the system is very important. If it is just 20 or 30K, that's usually no big deal, and it's doubtful you will starve out any other appliances.

When doing Tankless heaters, this is BY FAR the most important part of the install, and more often than not, plumbers are blowing warrantys left and right because of not properly gassing the unit.

You need to record all the gas appliances and their BTU's
Next, draw a rough lay out with distances and gase line sizes....you may have to crawl under... or up in the attic, but this is important. Do you have a monometer? It measures water column and I use mine to back up what my math had predicted. Sucks butt when I get that one wrong

So basically if it is a small but rating that your BBQ wants, I doubt it would be an issue. You want to throw a commercial stove in, or a tankless heater in....different story.

And if you don't have the available BTU's you will need to run a new gas line from the meter to the house. Average meter WC in my parts is about 8"

Tom M

Yes I know how to calculate total BTU and existing feeds but according to the code you would have to resize the whole system. I have no meters for testing so I am in the dark. I am interested in how to consider a price when dealing with my plumber. If a home owner asks me for a gas fireplace I need to realize whether or not my plumber is going to resize the whole system or extend a line. IS THAT THE COMMON PRACTICE FOR THIS?

JamesNLA

Gas fireplace, 20K for a standard blu-flame unit. I would probably just branch out and call it a day. For something that small, I can't imagine an inspector failing you on that because you are undersized. If the house goes over budget on gas from a 20K pit, than maybe the gassing should be redone.

If it was just a branch off a 1" or 3/4, less than 10-15ft your looking at about 4 hours or so, plus materials. bout $550 or so.

You don't need to redo all the gassing even if you are over the available BTU output of the system. Gas meters will/should keep 7" of WC at the output of the meter. So worst case, he needs to run a new line from the meter to the pit. But if that needed to be done, the gas lines for the house and the intended design has changed from the original build. Can't keep adding more electrical appliances to a house, sooner or later one needs an upgrade, same thing.
20K ought not blow over the design.

Monometer is about 90 bucks, but if you really have no need, than why bother? However with that tool, you can easily check to see if someones actual system is at the right pressure.