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  • Leaking black tank flush

    I have a 2019 Transcend 28 MKS. Has anyone has an issue where the fittings to the Black tank flush, located behind the shower, leak when they flush their black tank? I have used this before and did not notice a leak. This time it left the front of my trailer with standing water on the floor. Any thoughts on replacing those fittings without taking it to a dealer and losing it for a month or two?

  • #2
    Originally posted by bschopf View Post
    I have a 2019 Transcend 28 MKS. Has anyone has an issue where the fittings to the Black tank flush, located behind the shower, leak when they flush their black tank? I have used this before and did not notice a leak. This time it left the front of my trailer with standing water on the floor. Any thoughts on replacing those fittings without taking it to a dealer and losing it for a month or two?
    Almost every time I comment on a plumbing thread I get it wrong, so I'm just going to welcome you to Grand Design's Technical Forum and leave the technical response to the people who know plumbing.

    One of them is fellow moderator Cate&Rob -- hopefully he'll be along soon. There's many other forum members with a lot of experience in this area, so I'm sure you'll get some valuable input soon.

    Again--welcome!

    -Howard
    Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

    2017 Ford F-350 DRW, '19 315RLTSPlus

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    • #3
      bschopf
      The device behind the shower wall is a “vacuum break” to isolate your black tank from the fresh water line used to flush it. A small drip from this valve is “normal”. Standing water on the floor is not. The fittings to this valve are hand tightened. I would first make sure that these attachments are not loose. (This is the most likely cause of the situation that you describe).

      Rob
      Cate & Rob
      (with Border Collies Molly & Angel + Kitties Hazel & Elsie)
      2015 Reflection 303RLS
      2022 F350 Diesel CC SB SRW Lariat
      Bayham, Ontario, Canada

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      • #4
        Thank you, I will tighten and pressure check it. I have PEX fittings and a crimp tool. Is it a bad idea to make all of these fittings watertight?

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        • #5
          Originally posted by bschopf View Post
          Thank you, I will tighten and pressure check it. I have PEX fittings and a crimp tool. Is it a bad idea to make all of these fittings watertight?
          Of course . . . all the fittings should be watertight. Part of the problem (much discussed on other threads) is that crimping a soft hose to a Pex fitting with a Pex clamp does not guarantee a permanent watertight connection. The ID of the hose is too big for the OD of the Pex fitting. Start by hand tightening the threaded connections and observe for leaks.

          Rob
          Cate & Rob
          (with Border Collies Molly & Angel + Kitties Hazel & Elsie)
          2015 Reflection 303RLS
          2022 F350 Diesel CC SB SRW Lariat
          Bayham, Ontario, Canada

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          • #6
            Thank you for the advice. I'll try that first.

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            • #7
              Originally posted by Cate&Rob View Post

              Of course . . . all the fittings should be watertight. Part of the problem (much discussed on other threads) is that crimping a soft hose to a Pex fitting with a Pex clamp does not guarantee a permanent watertight connection. The ID of the hose is too big for the OD of the Pex fitting. Start by hand tightening the threaded connections and observe for leaks.

              Rob
              Just curious would a standard hose clamp work better or do you have the same basic problem?

              Charles and Susan
              2021 Ram 3500 6.4 Hemi, 4x4 CCSB
              Andersen Hitch
              2021 Reflection 337rls

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              • #8
                Originally posted by ckreef View Post

                Just curious would a standard hose clamp work better or do you have the same basic problem?
                A standard hose clamp might be better . . . from the perspective that you can re-tighten it if (when) it starts to leak. The basic problem is that a 1/2" ID hose is too loose a fit on a Pex fitting. If you wanted to keep the soft hose, the correct fitting for this is a "1/2" hose barb". See this thread https://gdrvowners.com/forum/operati...rline-fittings and particularly my attachment to post 6 for what goes with what (in my opinion).

                Note that this is my opinion and not the position taken by Grand Design and explained at length by them in previous discussions. They build with soft hose crimped to Pex fittings because this meets all applicable RVIA requirements.

                Rob
                Last edited by Cate&Rob; 03-27-2020, 08:34 AM.
                Cate & Rob
                (with Border Collies Molly & Angel + Kitties Hazel & Elsie)
                2015 Reflection 303RLS
                2022 F350 Diesel CC SB SRW Lariat
                Bayham, Ontario, Canada

                Comment

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