At least it's not a beer bottle...

[John Arnold]

For those of you unfamiliar with Wawa, that's a Wawa water bottle there trapped in the wall next to the gas fireplace. Wawa is our major convenience store chain here in Philly.

[Stephen G]

not having a grommet protecting that wire from the sharp edge of the sheet metal too....

[Fred Weck]

not having a grommet protecting that wire from the sharp edge of the sheet metal too....
That's "Gastite" not a wire.

[Stephen G]

okay, the 'gastite should have a grommet to protect from the edge.

[Nick Ostrowski]

But what's protecting the water bottle?

[Jerry Peck]

But what's protecting the water bottle?

The water self-extinguishes when broken. ;)

Last week a roofing company here was replacing a roof on a house, after quite a bit of work had been done, the house exploded beneath the roofers ...

... yeppers, the roofers drove a nail through some CSST, the propane leaked out into the attic, began filling the living space below (no one home inside the home), the inside reached the ignition gas/air mixture near a pilot light ... boom!

The roofers were not injured, but the house was a total loss due to the fire (structurally, the blast did not demolish the house, but the resulting fire did).

[CHARLIE VAN FLEET]

was there feces found on the roof or roofers pants

[Jerry Peck]

was there feces found on the roof or roofers pants

Not sure (there were 5 roofers on the job when it blew), but we all know there was brown stuff in the pants of roofing company's owner. :)

What I heard on the news is that the house was not destroyed by the blast, but I just searched for the article on the internet and found it, the article says the walls were "completely blown away", but then, the article also says "by roofers who punctured a liquid propane line just below the roof" and that propane line had propane gas in it, not liquid propane as the article says, so who knows.

Ormond Fire Chief: Roofers punctured propane line in home blast - News (http://www.news-journalonline.com/news/local/east-volusia/2012/01/19/ormond-fire-chief-roofers-punctured-propane-line-in-home-blast.html)

Their insurance rates are likely to go up ... that roofing company is one of the larger roofing companies in this area, so that likely will not put them out of business, but I bet it would if it happened to a small roofing company.

[Stephen G]

Jerry, what is 'liquid propane ' used for, Air Conditioning, Ice, industrial...

[Jerry Peck]

Jerry, what is 'liquid propane ' used for, Air Conditioning, Ice, industrial...

Liquid propane is what is in the lower part of the tank, that is why they can only fill tanks to 80% - to allow that remaining 20% for the liquid propane to turn to gas, the top of the tank is gas. As the propane is used, more liquid propane 'boils off' (for lack of a better description) and becomes gas, keeping the gas in the top of the tank.

That's about all I know of that, I am sure that Bob Harper can add volumes to that with his knowledge, and correct what I've said incorrectly (if I have).

[Stephen G]

no your correct. Its the liquid part I am having trouble with. These guys are on the roof. Once the liquid leaves the tank its a gas, unless its lower than the tank or the pressure is low enough.
I am wonderin why its still in a very cold liquid state anywhwere near the roof, or the roofers...

[Jerry Peck]

no your correct. Its the liquid part I am having trouble with. These guys are on the roof. Once the liquid leaves the tank its a gas, unless its lower than the tank or the pressure is low enough.
I am wonderin why its still in a very cold liquid state anywhwere near the roof, or the roofers...

That was one of my points - it wasn't a 'liquid as the reporters stated, so maybe the walls were not completely blown out either. ;)

In looking at the photos in that link, it does look like one wall may have been blown outward - or - it fell outward from the fire and firefighting operations ... I just don't know. But don't believe everything you read. :)

[Galen L. Beasley]

no your correct. Its the liquid part I am having trouble with. These guys are on the roof. Once the liquid leaves the tank its a gas, unless its lower than the tank or the pressure is low enough.
I am wonderin why its still in a very cold liquid state anywhwere near the roof, or the roofers...

Propane is normally a gas but can be compressed into a liquid to transport and store. Unlike natural gas, propane is heavier than air and will normally pond at the lowest level it finds. The ignition source could have been in the basement even though the leak was in an attic space.

[Stephen G]

Yes, we established that. what is not known is what this line is doing on the roof. How did a roofer puncture a porpane line. To blame them for drilling or puncturing a hose/line we must know where it was installed. They were on roof, presumably roofing.
No mention of why an attic has an unprotected propane line running through it??? Spark can come from anywhere, but, for the roofers to have set this in motion asks many question.
In the end it is more than likley what Jerry P suggested. "Dont believe everything you read. ":) :)




Propane is normally a gas but can be compressed into a liquid to transport and store. Unlike natural gas, propane is heavier than air and will normally pond at the lowest level it finds. The ignition source could have been in the basement even though the leak was in an attic space.

[Dom D'Agostino]

Yes, we established that. what is not known is what this line is doing on the roof. How did a roofer puncture a porpane line. To blame them for drilling or puncturing a hose/line we must know where it was installed. They were on roof, presumably roofing.
No mention of why an attic has an unprotected propane line running through it??? Spark can come from anywhere, but, for the roofers to have set this in motion asks many question.



Maybe they shot a nail into a gas line, or dislodged a poorly installed fitting in the atticby working on the roof.

[Jerry Peck]

Maybe they shot a nail into a gas line, or dislodged a poorly installed fitting in the atticby working on the roof.

Dom nailed it ... er ... the roofers nailed it, Dom explained it. :)

[Bob Harper]

CSST must have adequate strike protection-period. That may be being clipped so it flops inside a stud cavity with strike plates at the floor and celing penetrations or it may require approved flexible metal conduit. In an attic, the gas plumber has the responsibility to anticipate 'reasonable' hazards to his piping. Even if a roof has already been installed on a new house, eventually it will get re-roofed where they may use longer nails so that should be anticipated.

BTW, LP stands for "liquified petroleum". Yes, the fuel is in a liquid state while under high pressure in the tank. Yes, you need 20% for vaporization and to act as a pressure relief. At the first stage or high pressure regulator, the freshly vaporized fuel cools off as it boils off more when it drops in pressure from ~100-150 psi typical tank vapor pressures down to 10 psi. From there, it travels to the second stage or medium pressure regulator where again it cools as it is reduced to 11-14 inches water column or just under 1/2 psi for the working pressure. If you undersize the system and try to draw off too much fuel, the regulator can freeze up. You'll see this effect on a high BTU BBQ grille burning full blast with the tank level low.

FYI, the discharge of the second stage regulator is the legal 'point of delivery' or where it switches from NFPA 58 to your local code, usually NFPA 54 or IRC Ch. 24.

Several cool videos online showing LP explosions inside structures. Typically, the house walls focus the force back up lifting the roof allowing it to vent out the sides over the walls then the roof drops back. Saw one where the sofa blew up into the air then landed on the roof. Only takes about 1-3 psi overpressure to blow a house apart.

Galen is correct about the properties of LP-heavier than air so it ponds looking for a source of ignition. Think of the mist on the moors in those English horror/ mystery movies. That's how LP behaves.
HTH

[Jim Luttrall]

There have been numerous cases of roofers damaging gas lines here.
Due to age of CSST installations and corresponding frequent hail storms re-roofing has exposed the issue to the AHJ's and they are now requiring better nail protection.

The most common area for the lack of protection here is as the CSST leaves the top plate at the exterior wall and enters the attic.
In this area the tubing is usually tight against the decking as it makes the turn from vertical to horizontal.