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Slightly different Q re cutting cast iron

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  • Slightly different Q re cutting cast iron

    I was about to rent a snap cutter to cut out a section of the 4" soil in my house (about 100 years old) when I saw an earlier post suggesting that old pipe, esp. horizontal (which this section is) would more likely shatter and sawzall is recommended.

    1. is this the general consensus? if so, glad i looked
    2. if sawzall, grins, i've been looking for an excuse to buy one. since use will be infrequent and money doesn't go on trees, do i need to go for the heavy duty 10+ amp? i want enough to do the job, but don't need to go crazy here.
    3. and finally, which is better, the grit kind of blade or metal cutting toothed blade.

    thank you all who reply. this is so helpful.

  • #2
    A 4" horizotal piece of CI pipe can get thin if it has not been properly graded and could crumble. The again it could be one tough piece of pipe. If it is a tough piece of pipe be prepared to go through a lot of blades to get the job done.

    Mark
    "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

    I never lost a cent on the jobs I didn't get!

    Comment


    • #3
      Why it shatters

      Cast Iron in a corrosive environment (and a lot of soils are) goes through a process called "graphitization". Basically what happens is that the iron is leached out by the soil and corrodes away, leaving only the high carbon content of the graphite. It can look like a new black pipe, but it only has the strength of a similar thickness of the same stuff pencil leads are made of.
      Because soil is not exactly the same everywhere, this usually occurs in different amounts in any given section of pipe or circumferance. An easy way to check is to carve at the surface of the pipe with a sharp knife. If the metal is good, the knife won't carve into it (Cast Iron is HARD). If it starts carving away material, leaving a glossy black surface, it is graphitized. (I use to xray pipes to check for this, and an xray really shows the amount of lost iron, even if the pipe "looks" pristine. The damage may only go a little ways into the pipe wall or may go all the way through it. As long as the soil is undisturbed around it and there isn't a large pressure change, the pipe functions well. If the ground shifts (a heavy vehicle driving over it, earthquake, or just excavating for repairs,) the stress can cause the pipe to break or blow a hole in it. A snap cutter will cause the pipe to fracture along the weakest route, so if its graphitized, it will break unevenly or shatter.
      A saw will cut it straight, and IF its graphitized, will cut it quickly. However, the weakness is still there, and you may end up with a leak just from the stress of backfilling the hole breaking the pipe after you are done. If you suspect a weak pipe, replace the whole section or plan on returning for repairs.
      my 2 cents.
      I am not a plumber. I did spend quite a few years x-raying pipes to determine their condition for infrastructure repair planning, and this was one of the conditions we specifically evaluated.
      Practicing at practical wood working

      Comment


      • #4
        Originally posted by Gofor
        Cast Iron in a corrosive environment (and a lot of soils are) goes through a process called "graphitization". Basically what happens is that the iron is leached out by the soil and corrodes away, leaving only the high carbon content of the graphite. It can look like a new black pipe, but it only has the strength of a similar thickness of the same stuff pencil leads are made of.
        Because soil is not exactly the same everywhere, this usually occurs in different amounts in any given section of pipe or circumferance. An easy way to check is to carve at the surface of the pipe with a sharp knife. If the metal is good, the knife won't carve into it (Cast Iron is HARD). If it starts carving away material, leaving a glossy black surface, it is graphitized. (I use to xray pipes to check for this, and an xray really shows the amount of lost iron, even if the pipe "looks" pristine. The damage may only go a little ways into the pipe wall or may go all the way through it. As long as the soil is undisturbed around it and there isn't a large pressure change, the pipe functions well. If the ground shifts (a heavy vehicle driving over it, earthquake, or just excavating for repairs,) the stress can cause the pipe to break or blow a hole in it. A snap cutter will cause the pipe to fracture along the weakest route, so if its graphitized, it will break unevenly or shatter.
        A saw will cut it straight, and IF its graphitized, will cut it quickly. However, the weakness is still there, and you may end up with a leak just from the stress of backfilling the hole breaking the pipe after you are done. If you suspect a weak pipe, replace the whole section or plan on returning for repairs.
        my 2 cents.
        I am not a plumber. I did spend quite a few years x-raying pipes to determine their condition for infrastructure repair planning, and this was one of the conditions we specifically evaluated.
        Nice tip Gofor! And from a non-plumber too! I've always known it can happen but never knew why and certainly had no test to determine the condition of the pipe. Seems fairly rare around here but it's nice to know there is a way to tell before you start cranking down on the snap cutters. Now I'm pretty certain that no plumbing contractor is going to invest in x-ray equipment to analyze pipe with, well, maybe Rick will but probably no one else, but that knife trick sounds pretty cool. It sounds though as if it's only useful with respect to buried pipe? I recall a 2" cast iron kitchen sink drain that I replaced about a year or so ago that was completely "rotten". KS drains are of course notorious for accumulating grease, food particles, etc. (they are really the nastiest drains in a house imo) do you think it reasonably possible that any of these items might have the same or similar "leaching" effect on the pipe or is strictly soil that would cause it?

        Comment


        • #5
          [quote=ECS] Now I'm pretty certain that no plumbing contractor is going to invest in x-ray equipment to analyze pipe with, well, maybe Rick will but probably no one else, but that knife trick sounds pretty cool. /quote]

          no, not i.

          1 thing i don't need.

          a concrete cutting chainsaw was the last big budget tool i bought. this will cut 12'' deep and straight corners without overlap. sort of like a real chainsaw, but with a diamond tiped chain.

          still think a 4.5'' grinder with metal cut off blade is the way to go. a sawzall is a very usefull tool, but not my first chioce for cutting cast iron. if the pipe is so weak that is cuts too easy, chances are the pipe is no good. especially a 100 year old pipe. a snapcutter with the proper technique will work fine on pipe that is still good.

          no more play money this month, april 15/17th is here

          rick.
          phoebe it is

          Comment


          • #6
            ok, let's recap (please)

            Let's see if I understand what i've heard from you folks

            if the pipe is bad, then i have to replace the entire section anyway.
            snap cutter better than sawzall (i don't have room to use a grinder)
            If the pipe is good, the snap cutter will work fine
            if the pipe is bad, the snap cutter may trash it, but if i had used a sawzall and cut it ok, i'd be setting up for trouble later.

            so, i should go get a snap cutter and give it a shot.

            that about right?

            Comment


            • #7
              snap cutters will break the 100 year old pipe. a sawzall is not bad, a grinder is my choice. it doesn't require much room if you cut a window in the top of the pipe. this way you cut from the inside.

              it the pipe is in the dirt, the dirt is what holds the pipe together. don't disturb it and it will remain the same as before you found it.

              if the pipe is above ground, the outside appearence is the indicator to what condition the pipe is in. if the pipe is pitted, it's shot. a snap cutter on 100 year old pipe is not my first choice. a grinder is.

              if you need to rent a snap cutter $30.00, just buy a 4.5'' grinder instead with 1/16'', 1/8'' metal cut off wheels. also a good pair of goggles.

              rick.
              phoebe it is

              Comment


              • #8
                snap

                Well rick, sorry i went and rented before i read yours. no, the snap cutter worked great; i had a nice clean section out in no time. more the thought of buying a new tool instead of a one-time rental.

                well, thanks all for the input, even if i guess i did go a diferent direction. now to putting everything back together. hope it goes as smoothly as the first step.

                Comment


                • #9
                  I use a recip. saw to cut CI, but I'd like to hear from those of you that use a grinder, how do you use it if the pipe is up against something like a stud or joist or lying in water/sewage.

                  I suppose you could go through the hassle of pumping out the water/sewage but it seems like a waste of time, although time is money.

                  This old dog is ready to learn a new trick!

                  Comment


                  • #10
                    I know you have already made the cuts and it went well but in my opinion instead of a snap cutter a ratchet cutter is a safer choice. You can slowly take up on the cutter and as you do that score the pipe OD by rotating the cutter much as you would when cutting copper pipe with a tubing cutter, but you only need to rotate it a few degrees, enough that that cutter wheels overlap. Making this score mark as you make the cut is pretty similar to the way CI was cut years ago using a hammer and chisel.... basically you would use the hammer and chisel to score a mark on the pipe OD 360 degrees around. You continued to do this, striking the chisel which was placed in the groove from the previous time until the pipe was 'cut' (split along the score mark). Takes some time but it works, I've done it, last time was in 1978.

                    On the subject of 100 year old pipe. Back then CI pipe could frequently be found with an uneven pipe wall thickness. It wasn't until they started to spin the pipe during the casting process that even pipe wall thickness was obtained with any consistency. Prior to this it was common to spec or order XH pipe to avoid the thin pipe wall of SVC weight pipe. If using SVC pipe it was a common practice to put the thin side towards the top when not in a stack so the thicker pipe wall would take the wear.

                    Here's a shortcut to the Cast Iron Soil Pipe Institute's 226 pg handbook all about CI pipe.
                    WARNIG: this is a 6.4MB 226 page PDF file, if you are on dial-up you may want to think twice.

                    If you read the history section in the beginning, the NJ towns mentioned are in my neck of the woods. Tyler Pipe bought out the Salem Pipe foundries in located in both Salem and Bridgeton, NJ in the 1960's I think. Salem Pipe had been making CI pipe and fittings for many, many years, it is closed now and a Superfund Site.

                    Up until WWII, KRUPP in germany manufactured CI pipe and fittings which they shipped here along with Railroad tires (AKA wheels) and rails and many other steel products until the american steel industry grew and pushed them out. If you ever see a CI fitting with the KRUPP logo (three interlocking rings) which represented the railroaad tires, it is something of a rairty. I have seen a few in some older homes in the area.
                    Last edited by Bob D.; 04-14-2006, 08:05 PM.
                    ---------------
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                    ---------------
                    “If I had my life to live over again, I'd be a plumber.” - Albert Einstein
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                    Comment


                    • #11
                      how you tell an amateur from a pro

                      bob -- actually i was using a ratchet cutter. you're right, especially in a tight space like i was working in, it's a huge plus. failing to call things by their right name is a big mark of the amateur. how many times have you gone to the supply store and asked for that widget that goes between the thingies, like i do all the time.

                      by the way, given your history lesson, mine was made at monitor iron works. i'm in baltimore, btw.

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