dslreports logo
site
 
    All Forums Hot Topics Gallery
spc

spacer




how-to block ads


Search Topic:
uniqs
11736
share rss forum feed


Quiglag
God is Love
Premium
join:2004-09-19
Ontario, CA

Cutting gas line

My dad wants to install a tank-less water heater to replace our very old existing water heater. I guess it calls for 3/4" pipe but it is currently 1/2". In order to get the 1/2" out we would need to cut it.

So here is the question. Is there any danger in cutting the gas pipe after the main valve is turned off?

Thanks
--
\o/ My Website | Check Out My Gallery



SandShark
Long may you run
Premium,MVM
join:2000-05-23
Santa Fe, TX
kudos:3

I take it you're worried about the residual gas still in the pipe? What tool are you going to use to cut the pipe? A pipe cutter, reciprocating saw (Sawzall)? How much pipe are we talking about?
--
• • • - - - • • • | Hunt's Treasure



Quiglag
God is Love
Premium
join:2004-09-19
Ontario, CA
reply to Quiglag

He will probably use a reciprocating saw. He only has to make one cut, then after that they can be unscrewed. It is only a short amount that is 1/2" the rest of the house is 3/4"

Thanks
--
\o/ My Website | Check Out My Gallery



Ken
Premium,MVM
join:2003-06-16
Markle, IN
reply to Quiglag

I've done it before, what you want to do is open the line up and let it air out for a while. I saw a gas company employee once use a match to clear a line, and it just made a small poof out the end. I wouldn't try it myself, but cutting the gas line isn't really that dangerous. Just to be safe though I would let the line air out.
--
Business: MerrittConstruction.com | Personal: KenMerritt.com | Xbox Live:KENMERRITT COM


robbin
Premium,MVM
join:2000-09-21
Leander, TX
kudos:1
reply to Quiglag

He should be able to start at the water heater end and take it apart unless you are just talking about cutting a piece to get it out of the space it's in.



natedj
Elected
Premium
join:2001-06-06
Columbia, SC
Reviews:
·AT&T U-Verse
reply to Quiglag

I've been toying with the idea of replacing my unit to a tankless one but when my water-heater was up for renewal I chickened out and simply replaced it.
There are two types that I know of, an electrical unit and a unit that uses both electric and gas. Can you post some pictures and as the work progresses.
--
Good judgement comes with experience...Experience comes after bad judgements



jack b
Gone Fishing
Premium,MVM
join:2000-09-08
Cape Cod
kudos:1
reply to Quiglag

You really should not use any electrically powered tools to cut the pipe, since there is still gas in the line even with the main off. A sawzall has ignition potential.
Use a wheel cutter or a hacksaw, these are the preferred (safest) methods.
Before all that, you have to research the gas requirements the tankless heater needs. Some of these take up to 175,000 BTU/hr, and if all you have is a 3/4 inch gas line, it won't work right.
--
~Help Find a Cure for Cancer~
~Proud Member of Team Discovery ~



mattmag
Premium,ExMod 2000-03
join:2000-04-09
NW Illinois
kudos:3
reply to Ken

said by Ken:

I saw a gas company employee once use a match to clear a line, and it just made a small poof out the end.
Ever watched them *weld* gas lines together while they are still charged with gas? I was quite amazed to see that operation, and even more so when they told me it was a common operation.

Better them than me....

Geebo

join:2004-10-18
Fort Wayne, IN
reply to jack b

Click for full size
line size is fine see chart


jack b
Gone Fishing
Premium,MVM
join:2000-09-08
Cape Cod
kudos:1

The piping capacity table I prefer to use is a bit more conservative, plus you have to factor in pressure drop imposed by fittings and valves.
That prevents problems down the road.
--
~Help Find a Cure for Cancer~
~Proud Member of Team Discovery ~



r81984
Fair and Balanced
Premium
join:2001-11-14
Katy, TX
Reviews:
·row44
reply to Quiglag

Natural Gas is only explosive if it is only 5%-15% of the atmosphere. If it is more than 15% then there will not be enough oxygen for it to burn.

Cutting into a pipe with 100% natural gas will not cause an explosion.

The presure should be taken out of the pipe first because if there is a spark and gas shooting out of where you are cutting it could flame up until the pressure in the pipe is dissipated.
--
»www.ryanoneill.us



Candoo3

join:2005-01-24
reply to Quiglag

said by Quiglag:

My dad wants to install a tank-less water heater to replace our very old existing water heater. I guess it calls for 3/4" pipe but it is currently 1/2". In order to get the 1/2" out we would need to cut it.
I guess a quick question here would be, if you cut the 1/2 line, how are you going to connect the 3/4, in lieu of the 1/2 ? The 1/2 pipe must go back to a 1/2 female fitting, yes? Unless the system specs that you HAVE to use 3/4 all the way, you could just use a 3/4-1/2 reducer at the tank end.
Also, a common practice in use, is to use solid pipe to a near proximity of the equipment, then with flare fittings, use flexible copper between the pipe and the equipment, as long as it is protected from damage.

robbin
Premium,MVM
join:2000-09-21
Leander, TX
kudos:1

He has to change the 1/2" out because the tankless water heater requires more gas volume than 1/2" can supply. All of the 1/2" has to be replaced with 3/4".



iamchas

join:2001-12-06
Antioch, IL
reply to Quiglag

I had a tankless water heater put in a few years ago and had to go through the same thing with the gas pipe. In my case, we went back to the union where the 3/4" gas pipe that came into the house stepped down to 1/2" and replaced the 1/2" T with a 3/4" T. There was no cutting involved.



evgray

join:2003-05-19
Fort Scott, KS
kudos:2

I would use the preferred hack saw. Did you also take into effect that you have to have a larger size flew pipe for the new tankless water tank? The ones that I looked at had a 5" flew pipe as opposed to a 3". Just make sure that you have enough for a new flew.



traker1001

@mchsi.com

tankless heaters require a 6" Diameter insulated flu pipe directly vented out the wall, And cannot share a flu.


ke4pym
Premium
join:2004-07-24
Charlotte, NC
Reviews:
·VOIPO
·ooma
·Verizon Broadban..
·Northland Cable ..
·Time Warner Cable

said by traker1001 :

tankless heaters require a 6" Diameter insulated flu pipe directly vented out the wall, And cannot share a flu.
That's not entirely true. Several of the models I'm looking at (mostly from Rheem) require a 4" flu or less.


Casual User

@spcsdns.net
reply to Quiglag

What a professional will do will be different than what advice you should potentially follow.

Yes, I have welded on a gas filled line, and yes, I knew what to do if the #### hit the fan. Most don't. I don't recommend anyone to do that without training.

Cut the 1/2 inch line out with a tool that does not provide an ignition source. Right now it is unknown if you are in an enclosed space or not, but Murphy's law is pretty relentless.

If I was in an enclosed space, I would make sure the house was being aired out, lots of ventilation. The amount of residual gas will make a smell.

Make SURE you know how to turn off the gas valve. I have known of people to turn "off" the grease fitting on the house valve, and then open up the piping inside the house. Actually, I didn't see that last part....I was on a cleanup crew after the house caught on fire....

Remove all ignition sources. Etc etc etc. Did I mention ventilation?

The gas company may do the valve on/off for free.

Also, when putting stuff back together, provide mechanical support for the lines, accessible appliance valves, teflon tape (or equivalent), and place a soapy water mixture over the threads/fittings after assembly and the gas is back on.

Good luck!



Splitpair
Premium
join:2000-07-29
Cow Towne
kudos:3

3 edits
reply to Quiglag

said by Quiglag:

So here is the question. Is there any danger in cutting the gas pipe after the main valve is turned off?

Thanks
I'd be real careful in messing with the main gas valve as most are on the high pressure side (30-50 psi) of the regulator very tight to operate and if in the process you break off the feed line or the valve begins leaking you are going to be in a in a world of crap.

Also you must do a full pressure test of the new work and should test the entire system prior to re-opening the valve and that will require you isolate/remove the meter from the house line to pressurize those pipes for the test.

Personally if you are questioning how to cut a gas line you probably shouldn't be doing gas work and need to hire a licensed plumber or gas fitter to do the job. The home you save will be your own. If you insist on DIY'ing it find a copy of NFPA 54 and 58 and become intimate with the contents of both of those books before proceeding.

Wayne
--
If you cannot fix it with a buttset and some beanies you ain't a technician.


Splitpair
Premium
join:2000-07-29
Cow Towne
kudos:3
reply to Quiglag

BTW in order to cut the line you need to open it at both ends and ventilate the pipe by running compressed nitrogen CO2 or as a last resort air through it from the inside to the outside of the home. If it is natural gas it will rise so be sure to provide plenty of ventilation as you don't want it collecting in the attic and keep in mind propane is a little more dangerous as it will puddle without good ventilation. Either way be very careful.

Wayne
--
If you cannot fix it with a buttset and some beanies you ain't a technician.



traker1001

@mchsi.com

The real question is how are you going to re-thread it, I don't know about where you are, But around here the only gas line we are allowed to use is Black Galvenized Steel pipe. That stuff is a real paint to rethread, Even near impossible for someone who doesn't know what they are doing.



Quiglag
God is Love
Premium
join:2004-09-19
Ontario, CA
reply to Quiglag

Thanks for all the replies. There is only maybe six feet of 1/2" pipe that needs to be replaced. I don't think pressure should be a problem, as the only other thing that uses the gas, is the stove and the dryer. As I said in the first post, I was asking this question for my Dad. In the end it is up to him what he wants to do.

Thanks again.
--
\o/ My Website | Check Out My Gallery