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  • #16
    Re: Damaged threads on pipe

    Originally posted by PLUMBER RICK View Post
    don't do it. the pipe is already coated. the city protects their underground.

    rick.
    One other note. If the city is using poly or plastic pipe to the meter...That is there protection. Plastic is not subject to metal considerations. They are doing nothing to protect your system.

    Steel underground pipelines do require cathodic protection by some jurisdictions. I don't see anyway it is a bad choice.

    Comment


    • #17
      Re: Damaged threads on pipe

      Originally posted by blue_can View Post
      I guess I did not understand some of Kevin's post. So you are saying this should only be done if there is a dielectirc union somewhere between the city incoming pipe and the house pipe. If that's the case I assume the house pipe is another metal since there is no point of using a dielectric union otherwise - or is there?



      I did not follow this. Where and why?
      Steel distribution pipe lines require cathodic protection. If the city system is steel then they are providing protection. I will flip a dual headed coin that they are using plastic. By using plastic the city is protecting themself and not providing protection to you.

      Your plumbing sytem will be bonded. Your gas pipe system will be bonded. There will be common bonds between the appliances. If you attach from your side of the meter, all of that bonding will be sourced against any failure in your steel pipe protection. If your wrap and coatings are perfect no problem. They also need to stay that way after backfill. If there is one failure...then all of the bonding potential will act on that spot and burn a hole through the pipe.

      The dielectric union should be located on the outlet side of the meter and be present before the pipe goes underground. It should also be at a point of the system that serves no other points of use other than those the underground portion is serving.

      Or you can use plastic underground and set a riser.

      Comment


      • #18
        Re: Damaged threads on pipe

        I guess I still don't follow. As far as I know electrochemical corrosion occurs due to direct contact between two materials and some liquid. In the case of the buried pipe that would be the pipe, soil and the moisture. Since there is no physical contact between the ground rod for the rest of the home and the buried pipe how is this going to contribute to the corrosion in the buried pipe. There may be a potential difference between the ground rod for the home and the buried pipe resulting in a net current flow to the pipe from the ground rod but it is not via the electrolyte. So I'm not sure the dielectric unoin is going to help.

        Is this a recommended procedure by code. If so it's probably correct although it's not obvious to me at the moment.

        Comment


        • #19
          Re: Damaged threads on pipe

          Originally posted by blue_can View Post
          I guess I still don't follow. As far as I know electrochemical corrosion occurs due to direct contact between two materials and some liquid. In the case of the buried pipe that would be the pipe, soil and the moisture. Since there is no physical contact between the ground rod for the rest of the home and the buried pipe how is this going to contribute to the corrosion in the buried pipe. There may be a potential difference between the ground rod for the home and the buried pipe resulting in a net current flow to the pipe from the ground rod but it is not via the electrolyte. So I'm not sure the dielectric unoin is going to help.

          Is this a recommended procedure by code. If so it's probably correct although it's not obvious to me at the moment.
          Ok we have the first part understood as 3 parts of the elements needed.

          The city is not providing protection; your gas pipe sytem is bonded by the ground rod. What is going to give up first? The rod or the steel?

          The pipe is most certainly connected physically to the ground rod. Look at your water lines and see if there is a bonding lug. Look at the gas lines and see if there is a bonding lug. They all go to the same point. Look at a gas fired range, dryer, or other 3 pronged gas appliance. That bonding occurs there too. The entire mass of the system begins to operate as a little battery.

          In reality if you don't seperate the underground steel, then it becomes a ground rod as well, at any point of exposure. All of the house system bonded back to the electric panel comes back to the same bond. The pipe also gives itself up faster than the rod just like an anode. That causes the burning.

          Did that help any yet?

          Comment


          • #20
            Re: Damaged threads on pipe

            LOL - not really. I'm still not exactly sure what you are saying. If you are saying that current will flow to the ground rod via the buried pipe and the dielectric unoin will prevent that I cannot see it. The resistance from the buried pipe to the soil just next to it will provide a much smaller resistance than all the way back to the main ground rod used for bonding the home. So I still cannot see the use for this union.

            If you draw a diagram showing the system, the potentials, the current flows, how the corrosion occurs and how the union will prevent it, it may be clearer. .

            I agree about the plastic - if that's what the gas co is using then I guess there won't be any protection there.

            Comment


            • #21
              Re: Damaged threads on pipe

              As for code in your area...most likely it is not required.

              Those are natural gas guys talking and they are less likely to be aware of this situation. They pipe it and forget it based on the fact that a leak will rise and disperse causing few ramifications. The LP guys actually consider that to be lazy. We deal with a settling gas and must take more procautons. No leak is acceptable.

              Personally I would never use steel underground unless it was a liquid line and I had no choice.

              Comment


              • #22
                Re: Damaged threads on pipe

                the problem is dis similar metals (electrolysis) and the same action that a Die electric fitting helps with, is the same thing that can eat up pipes that do not have a anode on them,

                If a copper or copper coated ground rod is used, and you have steel pipe and the two are bonded, and depending on soil types and moisture, you essentially making a battery, “Galvanic Cell” in the soil, and it is what happens is similar to Electroplating it takes away from one metal and transfers it to another, so when you have the copper rod and the steel it take from the steel and transfers it to the copper or tries to, so the anode is lower on the scale than what the steel is and it takes from the anode instead of the steel,

                this is why pipe is galvanized, as it has the anode as built on protection on it, it sacrifices it self first and protects the steel in the process,

                the gas company actually apples a current to there system (or they do here) that counter acts the possibility of the steel pipe corroding, due to the electrolysis that can be created do to dissimilar metals, and bonding and grounding requirements.

                the simple is the anode is easy protection from corrosion,

                this paper is on tower anchors but explains it fairly simple,
                http://www.itrainonline.org/itrainon..._corrosion.pdf

                if properly wrapped there is little chance of the galvanic action taking place,
                Push sticks/blocks Save Fingers
                ~~~~~~~~~~~~~~~~~~~
                "The true measure of a man is how he treats someone who can do him absolutely no good."
                attributed to Samuel Johnson
                ~~~~~~~~~~~~~~~~~~~
                PUBLIC NOTICE: Due to recent budget cuts, the rising cost of electricity, gas, and oil...plus the current state of the economy............the light at the end of the tunnel, has been turned off.

                Comment


                • #23
                  Re: Damaged threads on pipe

                  http://www.elkgrovecity.org/document...es_P-05-26.pdf

                  I found this link that may help and is more direct to your area and situation.

                  Comment


                  • #24
                    Re: Damaged threads on pipe

                    Thanks for the replies BHD and Kevin. Good writeup by BHD although I still don't see any explanation about the dielectric union (or maybe I missed it). That document Kevin put up does show it but it has no explanation why it is there - more like a code thing. I was glancing through the gas code handbook last night and I could not see any mention of this. Not seeing any reason to this I probably will not be installing one - but having said that I probably will just stick to the coated/wrapped pipe - I guess very few people are using aniything more advanced.

                    I have another quesion - I will have some coated pipe left over after running the underground portion. I was planning to use that for some of the exterior run (in place of galvanized) with galvanized fittings. Any problems/code issues with doing this. Since I have pipe left over I thought I would use it rather than get some galvanized. This is not at the meter end.
                    Last edited by blue_can; 07-01-2010, 10:16 PM. Reason: spelling

                    Comment


                    • #25
                      Re: Damaged threads on pipe

                      Originally posted by blue_can View Post
                      Thanks for the replies BHD and Kevin. Good writeup by BHD although I still don't see any explanation about the dielectric union (or maybe I missed it). That document Kevin put up does show it but it has no explanation why it is there - more like a code thing. I was glancing through the gas code handbook last night and I could not see any mention of this. Not seeing any reason to this I probably will not be installing one - but having said that I probably will just stick to the coated/wrapped pipe - I guess very few people are using aniything more advanced.

                      I have another quesion - I will have some coated pipe left over after running the underground portion. I was planning to use that for some of the exterior run (in place of galvanized) with galvanized fittings. Any problems/code issues with doing this. Since I have pipe left over I thought I would use it rather than get some galvanized. This is not at the meter end.
                      It is addressing a problem 500-miles to the North of you.

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

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

                      Comment


                      • #26
                        Re: Damaged threads on pipe

                        This is my understanding of the Isolation fitting, the gas company puts a charge on the line, that reverses the galvanic action that would normally occur, called "Impressed Current Cathodic Protection" http://en.wikipedia.org/wiki/Cathodic_protection see about a 1/3 down on the page,

                        and they have to Isolate there system from things that would drain off the current they have put in to it, (this was the explanation I was given by the gas company when I lived in town on Natural gas), if the current is not correct they go looking for things that have been leaned up against meters and try to find out what is draining the current on there protection system,
                        Push sticks/blocks Save Fingers
                        ~~~~~~~~~~~~~~~~~~~
                        "The true measure of a man is how he treats someone who can do him absolutely no good."
                        attributed to Samuel Johnson
                        ~~~~~~~~~~~~~~~~~~~
                        PUBLIC NOTICE: Due to recent budget cuts, the rising cost of electricity, gas, and oil...plus the current state of the economy............the light at the end of the tunnel, has been turned off.

                        Comment


                        • #27
                          Re: Damaged threads on pipe

                          out here the gas company uses a plastic/ nylon bushing 1'' x 3/4'' for residential installations. they always are a sore spot as the plastic never does really tighten.

                          using the proper pipe primer and 1'' 10 mil. tape with 2 layers along with sand to protect the pipe during backfilling will properly isolate the pipe from ground. the pipe is factory epoxy coated and the tape and primer are used cover the wrench scars and fittings.

                          hdpe plastic is the best of both worlds, but it requires special tools and expertise to install it. typically on a short straight run, it's more economical to go steel. on longer complicated non straight runs, hdpe is the trick.

                          rick.
                          phoebe it is

                          Comment


                          • #28
                            Re: Damaged threads on pipe

                            Originally posted by ToUtahNow View Post
                            It is addressing a problem 500-miles to the North of you.

                            Mark

                            Comment


                            • #29
                              Re: Damaged threads on pipe

                              Originally posted by BHD View Post
                              This is my understanding of the Isolation fitting, the gas company puts a charge on the line, that reverses the galvanic action that would normally occur, called "Impressed Current Cathodic Protection" http://en.wikipedia.org/wiki/Cathodic_protection see about a 1/3 down on the page,

                              and they have to Isolate there system from things that would drain off the current they have put in to it, (this was the explanation I was given by the gas company when I lived in town on Natural gas), if the current is not correct they go looking for things that have been leaned up against meters and try to find out what is draining the current on there protection system,
                              Okay I guess that finally makes sense

                              Comment


                              • #30
                                Re: Damaged threads on pipe

                                Originally posted by PLUMBER RICK View Post
                                out here the gas company uses a plastic/ nylon bushing 1'' x 3/4'' for residential installations. they always are a sore spot as the plastic never does really tighten.

                                using the proper pipe primer and 1'' 10 mil. tape with 2 layers along with sand to protect the pipe during backfilling will properly isolate the pipe from ground. the pipe is factory epoxy coated and the tape and primer are used cover the wrench scars and fittings.

                                hdpe plastic is the best of both worlds, but it requires special tools and expertise to install it. typically on a short straight run, it's more economical to go steel. on longer complicated non straight runs, hdpe is the trick.

                                rick.
                                Here's a funny thing - I recently been a HD a few times getting supplies. I've noticed that black vs galvanized debate here Two of the guys who work in plumbing (and used to be plumbers I guess) told me not use galvanized. Both mentioned the reason is that the coating could flake off and clog up gas valves etc. The guy at HD this evening told me that he had jobs not pass inspection due to using Galv on gas lines. I was going to use galv near the meter but now I'm confused. I was going to call the inspector and ask. Even more puzzliing is that I already have galv pipe leading into the house.

                                Comment

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