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Compression Tees

Discussion in 'Irrigation' started by HooKooDooKu, Mar 17, 2008.

  1. HooKooDooKu

    HooKooDooKu LawnSite Member
    Posts: 70

    What is the most likely failure mode of a compression Tee?

    Why would tying into an existing main with a union be better?

    A recent thread wandered a little into the subject of Teeing into an existing mainline. The OP had said he used a compression Tee, and board members quickly claimed that he'd be fixing that in a few years.

    Obviously, the best solution (when possible) is to expose enough pipe to bend it just enough to slip in a standard Tee. Presumably, the 2nd best solution might be the 4 ells trick.

    But one of the other suggested alternatives was a union. I'm curious as to why a union would be better than a compression tee. In both cases, you are relying on a rubber seal (so if that is the typical point of failure, the union wouldn't seem to obviously be better). Additionally, the unions seem like something of a negative because from my (extremely limited) experience, PVC unions must be lined up perfectly or they will leak.

    I guess another question would be, if using a union, how do you install that? The only solution I can think of (assuming a situation where the existing pipe can not be bent at all) requires two unions, one on each side. Glue the female sides to the two sides of the existing main line. Then, after getting the length of the pipe in the middle just right (perhaps 1/8" too short), quickly glue the male ends to the pipe to insert, quickly insert it, and close the unions before the glue sets.
  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,667

    It would be just as wrong to expect a compression tee to correct misalignment as it would a union(s) ~ There are some very good compression tees to be had, if you buy from waterworks suppliers. The failed ones we often see are much cheaper plastic ones. Going by weight of material alone, a schedule 80 union is better than a common compression tee.

    ULTRAPOS LawnSite Member
    Posts: 23

    I am probally never going to hear the end of this but i will sometimes use a slip fix to add a tee
  4. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,667

    On a non-pressurized zone, you'd probably be fine with a slip-fix. On a mainline with water hammer, not as fine. You should look for the Kwikrepair fittings, if you want to leave the rubber out of the connection.

  5. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    I agree....
  6. HooKooDooKu

    HooKooDooKu LawnSite Member
    Posts: 70

    I'll agree that you can't expect a compression tee to correct an obvious misalignment. But I would argue that a compression tee has the slightest amount of wiggle room a union just doesn't seem to have.

    But once again, when a "cheaper plastic one" has failed, what exactly went wrong? Did the female threads develope cracks? Did the rubber rot? etc?
  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,667

    Unions do have a bit of wiggle room, and I make use of it. I also like unions because I can usually move a pipe end enough to make a connection with a single union. It's all situation specific, but for a mainline connection, I'd only want a waterworks-quality compression fitting, if I used any compression fittings at all. If the pipes don't line up, they make elbows for that.
  8. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,976

    I hate to admit it, but I've glued unions. :hammerhead:
  9. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    Oh my my, now I need to find an appropriate pic, you union gluer. :dizzy:

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