Thawing Pipes with a Welder

Didn't want to hijack the other thread so I started a new one.

MeAnthony wrote:
Wow, that must have been something to see! :
Why would it only work with DC? You're basically creating a short circuit in which the pipe becomes the conductor/resistance/heat source, right? Essentially the same as a light bulb works but on a heavier scale? Not trying to dispute your statement, just trying to learn and understand the "theory of operation".

Thanks!



It was something to see........as a kid, I remember seeing this a few times. A local mechanic, welder, TV repairman, etc., etc. used to hook his old DC welder up to the back of his car and take it to where ever someone needed their pipes thawed.
Many homes and barns were fed from springs with long underground pipes. With so much plastic being used to day, you're not likely to see this much anymore.
His welders were all hand built by himself from large generators.
I remember one was powered by a Model A engine and another with a 6 Cyl. engine out of a '36 olds.
Of course, these were DC welders.
Why AC would not work, I haven't a clue.
My Dad had a Forney AC welder which came with a "carbon-arc" torch for heating. You could also clamp the carbon electrodes to each side of a frozen nut and the nut would turn red in very short order. So, why wouldn't AC work as well as DC for thawing pipes?

for thawing AC or DC does not matter . Watts of heat is watts of heat .

When i was growing up on the farm my dad had a welder thaw our pipes many times. It was about 250 yards to the windmill. It worked many times. One time it didnt work because my dad forgot that he had dug up a leak and replaced a section with plastic.

The most important idea is the duty cycle of the supply (welder) many welders rated at 250 amps have a 25% duty cycle at that output. This does not mean run it
for an hour and let it cool for 4 hours. The specs are usually in 5 minute continuous operation (not clearly identified very often). To allow it to be
successful, an amp setting derated to 100% duty cycle will work. Jim

Back in the mid 80's we had a couple of extremely cold winters and I thawed water lines 10 to 12 hours a day for three weeks. I
paid for a new 300 amp 100% duty cycle Miller Big 40. Friend of mine a few miles away bought a new 600 amp Lincoln and and paid
for it in one little town thawing the main lines for the town. We haven't had a winter like that in years and now most of the
lines are plastic.

Told as a true story at the time.

Cold snap in Seattle, 2 guys with an engine-powered welder were going around neighborhoods thawing pipes.

Did it at one place, then the welder operator yells at the guy under the house, "This guy doesn't like the price- Reverse the polarity."
Homeowner- "No, no, that's OK- I'll pay."

My dad helped a guy with doing that, he had a hand crank 4 cylinder Hercules on a Lincoln DC.

I spent 32 years doing water & waste water planning for small communities, so have a bunch of stories about water system freezing screw-ups. Probably the one that shows how important it is that prior planning is necessary follows.

In most of our part of the world, water & sewer lines need at least 6' of coverage to the top of the pipe to prevent freezing. One city put in many blocks of new water & sewer lines in existing gravel streets without much engineering assistance. (After all, it was just replacing old stuff with new, no problem our staff can do it without a contractor or engineer.)

Several years later the council decided to do a drainage study & pave & gutter all streets for surface drainage. First winter after the job was done, they ended up with several streets that had frozen water lines where freezing had never been a problem before. To make surface drainage system work, some street surfaces had to be lowered by a couple of feet. Subsequently, not enough cover was left on them to prevent freezing. Big expensive mess to solve a problem that could have been prevented with just a little foresite!

Spent a couple winter in the environs of Fairbanks AK, as a fireman. Hae to pass along this cautionary tale.

One fellow up there had the pipes freeze in his mobile home. Hooked up a "thaw box", and because results weren't instant, went to town. Seems the freeze was somewhere beyond the connection points, and the water boiled out of the pipe through open faucets. Came back to a fully engulfed home with a couple dozen of my fellows putting water on the remains from big trucks with flashing lights.

Only work on DC? I'm with B&D (as usual) on this one. Are you guys smarter than the engineers at Lincoln Electric? Once had a Lincoln Tombstone on which the 75 amp setting was clearly marked for thawing pipes. Obviously was AC only.

This is what my father and I used to thaw out water pipes when I was a Kid. This was back in the 1950's and 60's. This welder still is in
use today. very reliable.

Most welders duty cycle is spec’d at % of 10 minutes. Many of the engine drive welders are capable of 100% at full power or very close to.

As long as it gets hot the pipe does not care if it is AC or DC

(quoted from post at 08:42:45 11/06/20) Didn't want to hijack the other thread so I started a new one.

MeAnthony wrote:
Wow, that must have been something to see! :
Why would it only work with DC? You're basically creating a short circuit in which the pipe becomes the conductor/resistance/heat source, right? Essentially the same as a light bulb works but on a heavier scale? Not trying to dispute your statement, just trying to learn and understand the "theory of operation".

Thanks!



It was something to see........as a kid, I remember seeing this a few times. A local mechanic, welder, TV repairman, etc., etc. used to hook his old DC welder up to the back of his car and take it to where ever someone needed their pipes thawed.
Many homes and barns were fed from springs with long underground pipes. With so much plastic being used to day, you're not likely to see this much anymore.
His welders were all hand built by himself from large generators.
I remember one was powered by a Model A engine and another with a 6 Cyl. engine out of a '36 olds.
Of course, these were DC welders.
Why AC would not work, I haven't a clue.
My Dad had a Forney AC welder which came with a "carbon-arc" torch for heating. You could also clamp the carbon electrodes to each side of a frozen nut and the nut would turn red in very short order. So, why wouldn't AC work as well as DC for thawing pipes?

Click to expand...

earned something new that makes perfect sense. Doesn't get cold enough to freeze underground pipe very often around here but good to know. I use steel pipe around the outskirts of a house incase a shovel finds it. As dry as it has been around here this year the 18" deep pipe may freeze. Do you just use the normal welding cycle as a guide?
Thank's for posting.

My personal experience back around 1985, I was reading the operation manual for a vintage Forney tombstone and came to a page about thawing underground water pipes. I didn't have any frozen pipes at the time as it was summer, but that next winter my sister in law called me and said her water pipe from the well house was frozen, could I help?( my older brother was roughneck out in the north sea), and I remembered the welder deal so I retrieved the manual and read it again. The manual gave an example of how to attach the cables and then explained that heat was not how the ice was affected rather it was vibration that would crack the ice and that would allow liquid to move through to open the pipe. This was all news to me but no matter I loaded up the welder and some long extension cables and headed out to rural Southmayd Tx. With ice on the ground I stretched out the cables over a 100 ft from pump house to an outside hose bib,, and then powered that baby up. The welder complained but stood strong, groaning and fretfull, the sis n law said " I hope the house doesn't burn down" (Yea that helps x@%* sis) but I was checking for undo heat rise at several places and no real heat was found. 10 minutes nothing changing,15 minutes maybe this won't work...20 minutes ,,was that a drip?? uh look another drip! then a dribble and then success!! The water was not warm, the pipe was not warm the welder lived another few years. Good Times

Those old Forney’s never give up. My ex father in law used an AC welder to thaw pipe to his barn. I learned to weld with a Forney.

(quoted from post at 21:32:18 11/06/20) This is what my father and I used to thaw out water pipes when I was a Kid. This was back in the 1950's and 60's. This welder still is in
use today. very reliable.
<img src="https://www.yesterdaystractors.com/cvphotos/cvphoto62112.jpg">

Click to expand...

I think I might have mounted the gas tank elsewhere, LOL.