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Thread: Two Questions About PVC Pipe

  1. #1

    Default Two Questions About PVC Pipe

    I have been reworking my sprinkler system and that has involved cutting into the existing CL 200 PVC pipe to add or change fittings. Two things have come up:

    1. One of my re-routings requires that a pipe runs across another pipe at a 90 degree angle. The two pipes are touching each other. Will this cause a problem over time, such as expansion/contraction movements wearing down one or both pipes? If so, is there an approved method of dealing with this?

    2. The existing 1" PVC pipe near the valves is very discolored from being buried for eight years. I wanted to add a tee in the pipe. No matter how much I washed, sanded or primer-cleaned the pipe, it still remained quite gray looking. I just couldn't get it to look the original white color. I went ahead and glued the new tee in place. Will I have problems later on from a poor joint? Is there an approved method of cleaning an existing dirty underground pipe prior to solvent welding in a fitting?

    I look forward to your advice.

  2. #2
    Moderator & Master Plumber hj's Avatar
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    Touchin should not be a problem. I have excavated PVC pipes which have been buried for DECADES, and have never seen any of them become discolored because of being buried. Discoloration usually occurs when they are exposed to sunlight above the ground. You probably do not have anything to worry about, but only time will tell. The real question is HOW did you get the tee into the line?

  3. #3

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    Thanks hj for your reply.

    You can see the discoloration in the photo below. It appears that the soil has stained the PVC. The original fittings, as well as the new fittings and pipe, are pure white, whereas the existing pipe is stained gray.

    Any fitting in the photo that doesn't have blue primer showing is a new fitting I added. My goal was to move 5 sprayheads from a zone that was overloaded with 12 heads (second pipe from the top of the photo) to a zone that had 4 heads (pipe at top of photo). I was able to get the new tee in the pipe at the top of the photo by digging out about four feet beyond the elbow of that pipe (up from the left side of the photo) to give me enough flex to pull the pipe apart.

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  4. #4
    Forum Admin, Expert Plumber Terry's Avatar
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    If you can't lift up the pipe and insert a tee, you can also point some 90's up or sidewise and add a "loop" that pushes down onto the added fittings. There isn't always an option for digging that far, or cases when you are between two points that can't be moved.

    If you did your best to clean it, and used purple primer, you should be okay.

  5. #5

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    Quote Originally Posted by Terry View Post
    If you did your best to clean it, and used purple primer, you should be okay.
    I used clear primer, not purple. I thought the only difference with purple primer was the coloring to allow you to see where you had primed, or to prove that you had primed for areas that have a plumbing code that requires priming. I chose to buy clear primer because in working with existing PVC I want to see how clean the pipe becomes and I thought the purple coloring might prevent me from seeing that.

    PS. I just checked the can and what I have is clear PVC cleaner, not primer. I assume that it still does a pretty good job of preparing the surface for the solvent, though a clear primer would also pre-soften the PVC in addition to cleaning. In this case, I would expect that it is good that I used a cleaner, and not a primer, because I used a lot of applications trying to get the pipe clean and primer may have over-softened the pipe.
    Last edited by vivona; 09-15-2010 at 10:33 AM. Reason: Add PS about cleaner versus primer.

  6. #6
    Plumber jimbo's Avatar
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    I see nothing in your picture which I would worry about. Point is, it is sprinkers, outside. The downside is another dig if something fails. Don't lose any sleep over this. The pipes probably bonded just fine, with the primer and the glue. As for pipe crossing, I have seen AND installed bigger cluges than you have here, and never had any adverse consequences.!

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