I live in a home in Birmingham, AL that was built in the mid-fifties. I am working on correcting some problems due to improper work done by the previous owners and am starting to completely re-pipe my natural gas system that feeds a furnace, water heater, stove, gas dryer, and fireplace log. I would like to add some additional gas appliances in the future. I have done some research and have a basic understanding of sizing the piping according to the amount of gas and distances for the various appliances. Presently, there are three ¾” branch lines from the meter that are reduced to ½” to the appliances. I would like to run two ¾” or (preferably) one 1” line from my meter outlet, reduced to ¾” and ½” to simplify the system and supply present needs and future additions. I know this has been discussed before, but I wanted to be certain I understand that it will work. I don’t understand how the ¾” meter outlet can supply the larger line without changing the pressure (I am assuming the pressure is .5).

Here is a website that might prove useful. SDG&E - Business - New Construction (http://www.sdge.com/construction/elevatedpressure/)

Note there are two distict methods of distribution. The multiple headers and the manifold approach. Traditional distribution is about 1/4 PSI. This link talks about a 2 PSI distribution system.

Some appliances have their own regulators, namely the oven/stove.

With the parallel distribution mode, the frictional looses in the pipes are smaller and thus smaller pipes can be used.

With a traditional drop approach, large diameter pipes may be required. These are more difficult to work with and are more expensive and possibly not readily available.

I hope this helps a little.

Thanks for the quick response. I found the site you referenced when I was looking for information, but didn’t think it was applicable because of the higher pressure used before the regulator. It makes a lot of sense now that I see it again. Not to oversimplify, but the use of two (or more) ¾” runs from the meter (reduced to ½” before the appliance) would be like the manifold system and the use of 1” pipe from the meter to the reductions to ¾” and ½” is like the branch system shown. It looks like the ¾” inlet I have to the manifold or branch would not be a limiting factor in the total cfh available.

You have the idea. The length of the pipe probably has the greatest effect because of the larger pressure drop.

A 3/4 in main at 0.5 PSI does impose a limit. That limit would likely be smaller if the manifold started 1 foot from the meter than it started 200 foot away with 3/4 inch pipe. At some point the diameter of the 200' length would be comperable to the restriction. e.f a 36" diameter pipe won't buy you anymore than a 2" pipe might. Because of the meter diameter.

Frictional losses will increase as the CF/H increases.



Cost, ease of install and satisfying the design all have to be balanced.

I think I understand. It would probably be overkill, but I may come right off the ¾” meter outlet to a 1” T and run the two 1” lines for the first 30’ to the furnace, then to ¾” for the final 30’. The tables show that a ¾” line would be OK for the 100cfh the furnace uses, but the larger line would allow me to add the 40cfh gas fireplace log to that line with plenty of extra capacity. I would then run the second 1” line about 20’ and branch off with ¾” to the 40cfh stove, 22cfh dryer, and 75cfh water heater with extra capacity for the later addition of another stove in the basement and another gas fireplace log. I know it would be easier to explain if I posted a sketch, which I may try to do later. I’m on the way to the home center to see if they have a good selection of 1”galvanized (part of the run is outside) and black pipe and fittings, including reducing T’s and el’s. The price difference between ¾” and 1” shouldn’t be very much – I hope. Thanks again.