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how to thaw frozen water service with welder

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  • how to thaw frozen water service with welder

    I work for a water utility that is considering the purchase of a welding machine to thaw frozen water services. I have several questions:

    1. Is it safe to use a welding machine to thaw a frozen water service?

    2. What welding machine is best to use to thaw a frozen water service?

    3. Is there a max amperage that can be safley applied to a frozen water service? The pipe materials would be 3/4" to 2" copper tube and galvanized steel.

    4. What are the potential dangers?

    5. Is there some type of published guideline on this procedure?

    6. Who should do this work and what training or certification should be required?

    Thank you in advance,

  • #2

    I you don't get an answer here (doubtfull, BUT possible!) post your question on the AWS buliten board at

    ...from the Gadget Garage
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    • #3
      I have used up to 400A machines to do this and DC is the best. I like a clamp on amp probe. There are some dangers. The main one being thawing lines with multiple houses with electric service from the same transformer and city water systems. If there is a high resistance connection such as a rusted galvanized coupling in the line the current path may follow the electric grounding that is connected to it. Since the neutral is bonded to the ground at main entrance panels the use of high currents may overheat a ground wire that is within or passes thru a wall somewhere. It could even start a fire in another house, not just the one you are working on. What I usually do is discnnect the ground to plumbing bond at the house I am working on, use rubber gloves in case of currents on the ground wire when disconnecting. You should be then able to get some idea with an ohm meter if it is bonded elsewhere or it may show some reading thru a ground rod, maybe Terry L can help some here, but the idea is to seperate it so that electric currents cant be carried via the neutral line and using it as the conductor isteaf of a pipe. Nice thing about rolled copper lines, reduces this a lot. After a while instinct plays a part in how much to heat but an amprobe is usefull in setting heats and making sure its working right. Using less than a couple hundred A makes it slow (the reason to use 40 or less is that it wont overheat a number 6 ground wire) You need to keep an eye on the machine to keep it from overheating, not so bad as winter temps help. You need to keep pressure on the line and it melts a small film of water on the inside of the pipe and when it starts to flow the water will melt the ice plug out. Good heavy leads help. Now, having said some of this,,, insurance companies have a fit about doing this because of a few horror stories, there is nothing inheriently wrong with thawing lines provided its done correctly. Miller doesnt reccomend doing it any more due to the conditions they describe, I guess they figure the amount of machine sales due to this are not worth the grief. If you dont understand this ask some more or get an electrician to help explain it,, I am not saying to do it,, but it can be done. Galvanized steel heats quicker than copper. Its a strange thing sometimes,,, have heated away,,, nothing,, take welder off for 10 mins, hook up and heat again and it works,,, ha. Usually a 3/4 copper line 75 ft about 30 mins @ 200A depending on a couple of factors. I like to avoid heating thru soldered copper joints when I can unless I am sure they are full of water.


      • #4
        You can only thaw pipes at less amps than your welder is rated for 100% duty cycle. I think the Lincoln tombstone AC welder is rated about 40 amps for 100% duty cycle. It has a line with circle or dimond at 100% duty cycle point. Now days they only recomend doing this on pipes isolated from buildings.

        Sberry27 did great job covering the rest of the story .


        • #5
          Fix them so they do not freeze again. Kinda like the ice dams. Everyone goes apesh)t over them in the winter, but nobody takes the time to eliminate the cause of the problem. And guess what... they come back next year! I suppose if you're a maintenance worker that does keep some hours availible for you.


          • #6
            Most of the tombstones are rated 70A and some of the older ones had "pipe thaw" right on the label. Its a little slow at that power but it does work. I have even put them on in the morning and came back in the afternoon when using those machines. Used some old number 6 electric service entrance wire for cables,, ha. I like the muffler clamp U bolt idea. On small lines I use Vise Grips and connect to it or make last connection on a heavy fittling or lead connector. You wouldnt want to arc a hole in a copper line.
            Last edited by Sberry; 11-15-2004, 07:50 PM.


            • #7
              Ridgid makes a tool desgined for this called a KT 200 with 300 amps output,no duty cycle and works on a 15 amp circuit.Right tool for the job!


              • #8
                This I woud like to see. maybe 30 A???


                • #9
                  Ridgid KT200

                  Here is a link to the KT200 , seems like a nice tool to have.
                  Victor 310, J-28 Torch Setup
                  Thermal Arc 190S
                  Thermal Dynamics Cutmaster 51 Plasma
                  Andy's Place


                  • #10
                    sberry covered the dangers and hazzards involved pretty well. When all pipes were galvanized iron and power distribution was simpler this was a standard practice for water mains but even more for fire hydrant stubs . I worked for the works department when I was in school and we used to test each hydrant every saturday. These are deep taps with drainback provisions and they must work.
                    Frost would hit 7-8 feet under the paved streets due to the clearing the insulating snow . we would thaw up to 15 stubs a day in cold weather , Nowadays with copper pipes , plasiic house plumbing and all the complex grounding issues I doubt if you could get a licenced conteractor to try this a second time.
                    The last time i did this was on as feed from a well to the house . I unpluged the pump, disconnected the grounds, ( hydro ,phone and cable feeders all have separate grounds clamped to the water pipe in the same area), then unsrewed a union iin the house two feet above the concrete .
                    When I was about 10 min into the thaw I looked up at the power drop on the pole and saw steam coming from the neutral tie point. I shut off all breakers in the house except the 220 feeding my welder and finnished the thaw then called hydro to get the bad connection repaired.

                    The point here is that I did everyting possible to isolate the pipe from the electrical side and still had problems with ground currents even with the thaw current held to under 60 amps .

                    If you or your employer go forward with this confirm the insurance limits before you start .

                    If I remember correctly from 40 years ago there was a chart on the power source that gave recomended setings . I think we used 5 volts for every 100 feet of 3/4 pipe in the thaw loop that gave us 75 to 100 amps depending on the condition of the pipe. That works out to 3.75 to 5 watts per foot .just enough to raise the temp above freezing.
                    For copper pipe with its lower resistance you will need less voltage and get more current to get the same watts per foot ,
                    The ground problem is independant of the power source and is the biggest concern here .
                    Good luck


                    • #11
                      The reason the kt 200 only draws 15 amps is that its output voltage is 4.5 volts instead of 20 like a welder which not only makes it safer,but more efficient because current generates heat-not voltage.


                      • #12
                        Well er heat is the product of current times voltage so it really takes both
                        watts = volts times amps
                        or watts = amps sqared times ohms or
                        watts = volts squared divided by ohms
                        All formulas derive from ohms law .

                        The problem here is that to thaw pipes you must put current through them. To do that you need voltage proportional to the circuit resistance. The longer the pipe the more voltage needed.
                        It is the unintentional I squared R power in . ground wires that causes the problems.

                        You should not use a constant voltage machine to thaw pipes because it will not limit the current if the connected load decreases in resistance.

                        Assume for the sake of discussion that a particular frozen pipe needs 200 amps to thaw it .
                        A constant current welder may have a 400 amp capacity and 80 volt open circuit voltage. If you set the current to 200 amps and connect it across a pipe the voltage from one pipe connection to the other pipe connection will be 200 X 200 X pipe resistance. The welders terminal voltage will be controlled by the internal design of the welder to that value plus cable loss. .
                        Tthis means that if the kt 200 can put 200 amps into that particular pipe the voltage wiill be exactly the same as the welders loaded terminal voltage assuming that the same cables and connection points are used for both machines . On the other hand if the kt does not have enough voltage to push 200 amps into the pipe then it will not thaw the pip[e , The welder on the other hand will rsise the voltage untill 200 amps flows and thus it will thaw the pipe.


                        • #13
                          I dont know much about electricity but it seems you are only going to be able to get 1800 watts out of the wall and there isnt any more.


                          • #14
                            Originally posted by Sberry27
                            I dont know much about electricity but it seems you are only going to be able to get 1800 watts out of the wall and there isnt any more.
                            Not even that much. that is the must trip level.
                            The actual continiuous output of a 15 amp receptacle at high rated ambient is about 1320 watts. This ambient is the temperature in the breaker box not the outside ambient. That is why you get toasters ,kettles microwaves ect designedfor 1300 watts.


                            • #15
                              Yes, that was what I was actually thinking, it would have to be rated to run continious on a 15A circuit. I dont remember the readings on the last one I heated, it seems it was about 200A at 22v or so maybe a little less. It was at a casino and we had half the maint crew standing around and they had just got a new meter. I had a couple poor lead connects and they really show up laying in the snow,, ha. I had a couple of 100 ft 1/0 leads I lost in a fire and everytime I thaw now I wishing I had them back instead of piecing 50's. I should redo connectors before I need them this winter. Burning a couple small electrodes you dont notice but heating you do. I have done as much as 400 ft of 1 1/2 galv and it took about 2 hrs or less which is kind of amazing.