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Adding A Gas Line Branch
I live in a 50 year-old house in Northern
California. I have a lot of home improvement experience.
I want to add a gas line for a stove top. Because of limitations with the
existing line coming off the gas meter/regulator, I am considering running
a second line. There is a tee on the line going through the wall and it
looks like it would be easy to add this second line. what am I
overlooking? Any problems? Size of pipe? Should I contact the Gas company?
I am going to have a permit when I do this, but the city only provides
limited information.
Thank you,
Alan
Understandably,
I'm a little hesitant to offer any advice about do-it-yourself gas
plumbing. You must realize that the person doing the plumbing is
ultimately responsible for the quality and safety of the installation.
As for sizing... I'm not entirely sure of all the aspects of system
design, but I understand that 1/2" pipe can handle enough gas to
power appliances totaling 300,000 BTUs per hour. That's a lot of heat.
Most residential furnaces are rated in the neighborhood of 100,000 BTUs
per hour. I think that gas stove burners are rated around 25,000 BTUs
for the smaller ones and 35,000 BTUs for the larger ones. All together
the cooktop could demand perhaps 120,000 BTUs per hour. This can be
handled easily with 1/2" black pipe.
You need to be familiar with installing steel pipe and using pipe
wrenches. This isn't rocket science, but there are some finer points,
such as the degree of tightness. Like I point out in one of those
articles, steel pipe fittings are about half as tight as a car wheel lug
nut. I would guess that I tighten pipes to about 50 foot-pounds, which
takes a bit of muscle. If you crush the pipe, it's too tight.
You need to check every joint for leaks (with the gas turned on)
by spraying a little soapy water on them. Be alert when you turn on the
gas: Don't let anybody make any noise... the truly dangerous leaks may
be audible. Make sure your nose is working properly (don't do this when
you have a cold) and open some windows just in case. Since the gas will
have been shut off, all the pilot lights should be extinguished already.
A house full of gas is only dangerous if something sparks and ignites
it, but then, that's not a safe bet! A light switch can ignite gas.
Note that plumbers are required to pressure-test new gas piping by
capping off the outlets and pressurizing the system to (I believe)
around 30 PSI. The actual pressure in a gas system is only about 1/2 of
a PSI. I'm not sure what inspectors require when adding a branch line.
Proper thread lubricant compound is important. Use a compound that says
it's safe for gas lines. All valves need to be rated for gas. Some
valves have the letters WOG cast into the valve body. This stands
for Water, Oil and Gas. That's what I look for.
I always leave an extra tee fitting (or two) for future expansion. I
prefer to employ a union fitting somewhere so the line can taken apart
later. I always add a shut-off valve (the quarter-turn type) somewhere
on the new branch so I don't have to turn off the gas to the entire
house to fix some leaks.
Fixing leaks is the real problem. It's easy to have a fitting that is
not tight enough, and without a union somewhere upstream, you may have
to dissemble half of your work just to tighten one elbow.
And elbows are a pain in the butt, because they have to point in a
certain direction. This means that in order to tighten an elbow
"just a little more" you often have to turn it a full 360
degrees. This additional rotation can be difficult or damage a fitting.
I recently cracked a water shut-off valve this way. Luckily I had a
union fitting nearby and I was able to replace the valve no problem.
There is a solution to this dilemma, though, and it reveals the
subtleties of plumbing (I bet you didn't think there was anything subtle
about piping, right?) If the upstream sections of pipe are tightened
just enough (not too much, not too little) then when you are
cranking on that elbow fitting to make it rotate another full and
agonizing turn, the upstream pipe often turns along with it. This
is desirable, because it means that the fittings are approximately the
same tightness (your work is consistent) and the elbow fitting is less
likely to be damaged from excessive tightening. Thus, learning just how
much torque (rotational force) is enough is the key, and it's
very hard to explain. All I can say is: I believe it's about half as
tight as a car lug nut. Since I use a calibrated torque wrench to
tighten my lug nuts, I have become quite familiar with the feel of 100
foot-pounds. Maybe this would be a good time to buy that $100 torque
wrench you've been wanting. Every mechanic needs one. You do car repairs
too, right? <heh-heh>
I hope this information helps. I still recommend doing some more
research, to get the opinion of a true professional. I am not an expert.
I would recommend looking at some books that cover basic and
not-so-basic plumbing. One book I bought was Plumbing A House by
Peter Hemp, published by Taunton
Press, and sold on their website and at Home Depot. This is a good
contractor-oriented book that doesn't repeatedly whine "hire a
professional".
Bruce W. Maki, Editor.
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