Natural Gas Shut Off

After I had my house built, I noticed that the natural gas line to the dryer did not have a shutoff valve. The builder sent over a plumber to install one. Without turning off the gas, he unscrewed the end cap, doped up the threads, and screwed in a shutoff valve. Although it only took less than a minute, was this safe? This was located in the basement near the furnace and water heater, which could have provided an ignition point. I never had to shut off the gas to the whole house. For my information, where is the main shutoff for the gas?

Reply to
Edge
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mainm shutoff should be at meter.

yes its safe provided its completed fast. just like working with live electric lines, that safe too if done properly.

natural gas is lighter than air, and the amount lost small. so dont worry

Reply to
hallerb

Was this safe? No. Is it common? I wouldn't be surprised.

When I had my furnace installed, we discovered that the main shut off inside the house turned off the gas to all the appliances except the furnace. The pipe to the furnace was T'd before the main internal shutoff. In order to shut off the gas to the furnace, we would have had to shut off the valve at the meter outside the house, which would have required a service call to the gas company to turn it back on. We opened all the doors in the basement and the installer removed one section of pipe at a time, installing a nipple with a cap as he got the next section ready. Eventually he rerouted the pipe to where it had to go, with each section only being open for a matter of seconds. With the air movement from the doors open we barely smelled any gas during the process.

I will note that the installer determined which pair of pliers he would use to turn off the gas at the meter and kept them handy throughout the rerouting in case he had to turn the gas off.

Reply to
DerbyDad03

Why would the gas co. have to turn it back on if you all turned it off? The valve turns just as easy both ways.

s

Reply to
S. Barker

I had a similar experience - when we put in a gas stove in the kitchen, the installer had to run piping for it. Working backwards from where the stove was, he installed piping (including a shutoff) up to the point where he was going to tap in to the existing gas pipe. He then quickly unscrewed a connection and installed a T to serve the new pipe. As I recall, part of the time he just put his thumb over the open pipe end to minimize leakage. Nothing bad happened. -- H

Reply to
Heathcliff

See

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Recently the gas company was out to put a new meter on a new home. She installed the meter and opened a gas line inside the garage to purge the line. About thirty feet away was a lit cigarette.

The tech told me that the cigarette was "not hot enough" to ignite the gas. I was surprised by this comment.

Reply to
Oren

quoted text -

The installer looked at the meter and said it was the style that was required to be "reset" with a special tool before the gas would come back on. Yes, the valve would turn both ways, but that something else had to be done to actually get the gas to flow. I guess it's a safety thing - if the gas had to be shut off, then either something was wrong or you made a change and they want to inspect stuff before the gas can be turned back on. No one would just turn the gas off for no reason.

On the other hand, the installer could have been wrong...I'll call my gas provider when I get a chance just so I'll know.

Reply to
DerbyDad03

re: just like working with live electric lines, that safe too if done properly

Except that when working with live electric lines the results would not be as dramatic if something goes horribly wrong.

Let's take a worse case scenario - a solitary worker becomes disabled in the middle of the job - say from a heart attack. With live electric lines, there would be little to no damage, other than perhaps an injured/killed worker or a tripped breaker. However, if that same worker becomes disabled after opening a gas pipe, things could go boom if the conditions are right.

I know it's long shot situation, but to call it "just like" working on live electric lines might be a stretch.

Reply to
DerbyDad03

According to Oren :

A smouldering cigarette isn't very hot - puffing it makes it a lot hotter, and apparently methane has a rather high ignition energy compared to other gasses.

However, the explanation is probably not that.

Methane has a LFL (lower flammability limit) of 5.3% and a UFL (upper flammability limit) of 15%. It also has LEL (lower explosive limit) of 5.53%.

Which means that unless the methane concentration in air is between LFL and UFL, it won't ignite.

Gas lines past the regulator are also fairly low pressure, so opening it doesn't spew gas very quickly. Secondly, methane is lighter than air, so it goes up, rather than stick around.

An residential gas line venting in open air, is quite unlikely to ignite from something 30' away. Even enclosed in an open garage, it'd take a while to build up the concentration to the danger point - if there's any ventilation at all, it might not ever reach that concentration more than a few feet away from the vent point.

You still have to be careful - there could be wind patterns that push a plume to exactly the right place. And it depends on the gas. Propane is heavier than air. It will "puddle" in depressions and stick around for quite a while in low wind conditions. There was a propane tank car derailment around 40 years ago in the north end of Toronto, where the tank fully vented. Everything was pretty much under control, until the propane flowing down a small creek valley (very still air conditions) finally reached an open flame about half a mile away.

Can't happen with methane.

Reply to
Chris Lewis

Thanks. IIRC, she did state that striking a match would be hot enough to ignite the gas, but the concentration would have to build up.

Reply to
Oren

I'd wondered that also. I've shut off gas before the meter, just have to turn it on very very slowly until you hear the gas start to flow. And then leave it for several seconds, so the system pressurizes slowly.

Reply to
Stormin Mormon

The guys I've worked with call that "changing a valve on the fly". The way I saw it was to dope the threads as you unscrew the cap, so that the pipe is open for the briefest time possible.

Safe? Well, if it's done skillfully and quickly, it's not too bad.

Reply to
Stormin Mormon

Why? I've never heard that.

Reply to
Stormin Mormon

I have been told that natural gas is not chemically pure. It is a mixture of various natural gases - methane, ethane, etc. What the utility company does to ensure a uniform BTU, I don't know.

As for the low pressure of the gas line, I know that I have turned on the gas at a stove where it did not ignite immediately. The gas buildup from just waiting a couple of seconds before finally igniting produces a mini explosion that would singed my eyebrows if I were close enough. A plumber's face would be closer to an open pipe. I guess a good plumber will still have hair on his face.

Reply to
Edge

Besides UFL and LFL flash point is another part of the equation. Methane's is far below zero and a cigarette or match would readily ignite it. Static electricity, like from walking over a nylon carpet could ignite it. There is also autoignition temperature and it takes a very hot surface to ignite methane. The tech's comment about the cigarette was downright stupid.

Reply to
Frank

stove burners are mixers too, designed to mix air and gas for good burning. thats not the case with a open gas line.

gas companies do it all the time, as proof whens the last time your gas was shut off when they did repairs?

never in my case, really only occurs when water gets into gas lines. other than that gas up time must be 100%

Reply to
hallerb

I answered that questi Quote ...

The installer looked at the meter and said it was the style that was required to be "reset" with a special tool before the gas would come back on. Yes, the valve would turn both ways, but that something else had to be done to actually get the gas to flow. I guess it's a safety thing - if the gas had to be shut off, then either something was wrong or you made a change and they want to inspect stuff before the gas can be turned back on. No one would just turn the gas off for no reason.

On the other hand, the installer could have been wrong...I'll call my gas provider when I get a chance just so I'll know.

... Unquote

Reply to
DerbyDad03

For what it's worth, I was watching TOH a few weeks ago where they tapped into the gas main to run a new line to a customer. They used something very similiar to those needle valves you use to tap into a water line. It was more sophisticated in that they drilled the line first and then attached the valve, but the device they used kept the gas line sealed at all times. I know that's not a repair, but the point is that they kept the system both pressurized and sealed at all times.

However, I do have a question about your repair scenario: If they actually opened the lines and vented the gas to the open air during a repair, wouldn't there be a "gap" in any downstream gas delivery that would extinguish any pilot lights that were burning?

Reply to
DerbyDad03

That was the new service line to the residence that was being purged, not the main, so the answer is "no", they wouldn't have noticed.

As for the tap-in, sure they seal and are careful of sparks, too, but the main lines are at much higher pressure/volume than a single service line so they lose much more gas than the scenario here.

Reply to
dpb

Was it safe? I guess it was if your house is still there. As a licensed plumber I have done that many times but I would not have done it if the homeowner was there. The gas has a very potent smell that is much stronger then the gas itself. It's done that way to get the consumers to pay attention to a small leak. Ever fixture needs its own shut-off. The main gas shut-off is located outside the house where the gas main enters the house. It is illegal to for a gas pipe to enter any building below ground. Your gas meter also has a (2) gas shut-offs. One is for a lock when you don't pay your bills. Listen or call in to the Jack Hammer Re-construction show on Tuesday Morning 9:am to 10:am

888-321-7234 and
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Tomorrows show is about water treatment.
Reply to
Jack Hammer

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