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  • Black Tank Flush line access

    Hello
    we used our RV plumbing for 3 days. No plumbing issues.
    On breakdown to next location, we drained Hot Water Tank, and Low Level Points of water. The eventual issue didn’t appear, yet

    we hooked up and ran the Black Tank Flush, twice.

    We noticed this leak (shown below), first on the drivers side, then it moved to passenger side when we drove the RV off of leveling blocks

    there was a mobile RV Repair guy “in the neighborhood”, so with the promise of “lunch on us”, he came to inspect (but wouldn’t take the job). His advise is that we likely have a leak in the line from the black tank flush line. ((We’ve used this before with no known issue... ))

    he suggested unscrewing the outside fixture, pulling out a bit to see. We did this, and saw nothing. No water but also no view “deep” to the floor, where I more suspect the water to be.

    In the bathroom :
    We looked behind the draw in bathroom. We could see the hot water tank, and floor. No water.

    we removed that white small panel directly under the shower. Not much of a view, but no water seen

    we tried pulling the panel on the lowest cubbie, but didn’t succeed. We might try that again.

    What is the best access point to get in and look at the Black flush plumbing? and maybe fix. I feel like it’s the bottom cubbie panel. But the angle of even that seems like a total novice (me) would have a hard time getting to this.

    thanks in advance.

    grand design.
    Imagine.
    2600rb. 2021

    Attached Files
    Grand Design-Imagine
    2021 (1st Edition) 2600RB

  • #2
    as far as the fitting on the backside of the black tank flush hookup, if you don't have easy access to it inside the trailer then you can always unscrew it from the exterior wall and pull it out thru the exterior wall to check the fitting. There should be enough slack in the hose to allow for this. If that fitting is tight, then it is either a loose fitting on the tank or a cut in the soft hose from the tank to the hookup.
    Jeff and Debbie
    2021 Imagine 2250RK
    2015 Ram 2500 6.7 CTD Crew Cab Short Bed Factory Air-Ride Auto Level
    USMC Veteran

    Comment


    • #3
      Thanks. From the outside, we did unscrew the fitting and pulled out. All looked ok, for as far as we could see. No water from the hose/on the hose. I suspect it’s more closer to the tank where the line meets.

      thank you for your reply.
      Grand Design-Imagine
      2021 (1st Edition) 2600RB

      Comment


      • #4
        You stated that you drained the HWH. Did is it possible that the HWH drain let water get behind the wall? You may have to drop the coroplast in the rear and see if you can determine where the water is coming from.

        Between camping expeditions I do not drain the HWH if its a short time. I did learn to let the water run for a bit to flush the lines. Draining the lines gives a lot of opportunity for hard water to leave behind solid buildup.
        Joseph
        Tow
        Vehicle: 2024 GMC K3500 Denali Ultimate Diesel
        Coach: 303RLS Delivered March 5, 2021
        South of Houston Texas

        Comment


        • #5
          Originally posted by Chipster View Post
          What is the best access point to get in and look at the Black flush plumbing? and maybe fix. I feel like it’s the bottom cubbie panel. But the angle of even that seems like a total novice (me) would have a hard time getting to this.
          The black tank on a 2600RB is at the rear of the camper because the bathroom is at the rear of the camper.

          The black flush connection point is street side, rear of the camper.
          Click image for larger version

Name:	Flush Connection.JPG
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Size:	82.7 KB
ID:	49803

          Typically the black tank flush valve is behind the shower faucet.

          Click image for larger version

Name:	behind faucet.JPG
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ID:	49804

          Here's how it looks in my 315RLTS behind the faucet.

          Click image for larger version

Name:	Behind Faucet in 315RLTS.JPG
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ID:	49805
          If it's not there, a call to GD Customer Service to inquire where to look for the valve is what you might try. (Number is on business card, home page of this forum.)

          Please report back what you find out! The power of an owner's forum is helping each other by posting information.

          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

          Comment


          • #6
            Originally posted by Jlawles2 View Post
            You stated that you drained the HWH. Did is it possible that the HWH drain let water get behind the wall? You may have to drop the coroplast in the rear and see if you can determine where the water is coming from.

            Between camping expeditions I do not drain the HWH if its a short time. I did learn to let the water run for a bit to flush the lines. Draining the lines gives a lot of opportunity for hard water to leave behind solid buildup.
            Hello
            I appreciate the feedback.
            I am pretty sure not, because we trained that HWH many times, and even that day. The water didn't appear then
            It was only after we ran the Black Flush as the last step that we saw the water

            I'm still working the problem, so dont have 'my' solution yet.
            I will follow back on this and give an update.

            Thanks
            Grand Design-Imagine
            2021 (1st Edition) 2600RB

            Comment


            • #7
              Originally posted by howson View Post

              The black tank on a 2600RB is at the rear of the camper because the bathroom is at the rear of the camper.

              The black flush connection point is street side, rear of the camper.
              Click image for larger version

Name:	Flush Connection.JPG
Views:	1503
Size:	82.7 KB
ID:	49803

              Typically the black tank flush valve is behind the shower faucet.

              Click image for larger version

Name:	behind faucet.JPG
Views:	1339
Size:	60.9 KB
ID:	49804

              Here's how it looks in my 315RLTS behind the faucet.

              Click image for larger version

Name:	Behind Faucet in 315RLTS.JPG
Views:	1332
Size:	121.5 KB
ID:	49805
              If it's not there, a call to GD Customer Service to inquire where to look for the valve is what you might try. (Number is on business card, home page of this forum.)

              Please report back what you find out! The power of an owner's forum is helping each other by posting information.

              Howard
              Thank you for this.
              I did find the outside Black Tank Flush, and did check if the leak was there.
              I dont believe the leak on the 2600RB would be behind the Shower Faucets (but can't be sure it's not either).
              Faucets are inside the camper, an no water is inside the camper - just leaks out that back wall

              I'm still working the problem, so dont have 'my' solution yet.
              I will follow back on this and give an update.

              Thanks
              Grand Design-Imagine
              2021 (1st Edition) 2600RB

              Comment


              • #8
                Chipster It could have been some trash in the black tank anti siphon valve allowing it to leak slightly but then sealing after you cut the water supply to it. Campers and houses are terrible for cleanup in places you cannot see.
                Joseph
                Tow
                Vehicle: 2024 GMC K3500 Denali Ultimate Diesel
                Coach: 303RLS Delivered March 5, 2021
                South of Houston Texas

                Comment


                • #9
                  Hello All,
                  Thank you for the feedback, Very helpful for a newbie (me).

                  The leak is (or may not) be a leak after all.

                  1) The Black Tank Flush was not leaking at all. We had a tech come out and check that throughout.
                  2) The "leak" was from the Hot Water Tank, Pressure Release Valve. When we turn on the hot water, it would heat up super cold water.
                  This seems to expand, and the pressure release drips a small amount. This stops when the water cools down or the heater is not on.
                  The amount of water from this pressure is relatively small (drips... ).

                  Thanks again.
                  Grand Design-Imagine
                  2021 (1st Edition) 2600RB

                  Comment


                  • #10
                    Chipster I found that when first starting the HWH if you wait 10-15 min, then "burp" the hot side of a faucet you will get a blast of water, then normal flow. If you keep the HWH on and hot (less showers or large Hot water draws) mine would not leak again.
                    Joseph
                    Tow
                    Vehicle: 2024 GMC K3500 Denali Ultimate Diesel
                    Coach: 303RLS Delivered March 5, 2021
                    South of Houston Texas

                    Comment


                    • #11
                      Originally posted by Jlawles2 View Post
                      Chipster I found that when first starting the HWH if you wait 10-15 min, then "burp" the hot side of a faucet you will get a blast of water, then normal flow. If you keep the HWH on and hot (less showers or large Hot water draws) mine would not leak again.
                      Hey Joseph,
                      Thanks for this.

                      Mind if I run my process by you, and see if you see something wrong?

                      We are doing a long trip, with 30 stops. This 'drip' started around Stop 08.

                      My 'routine' is to drain the lines & Hot Water Tank between each stop, by opening the Low Level Points and letting the water out.
                      I'm doing this because of 'weight'.

                      When we get to the next stop,
                      1) I open the hot/cold faucet & connect the water source.
                      2) I let the faucets run until all the air is out.
                      3) I then shut off of the faucets, when no more air.
                      Done

                      Between Step #1 & #2,
                      I was opening the Pressure Release Valve, until all the air escaped and some water came out
                      I would then shut the Pressure Release Valve, and then go on w/ step #2 above.

                      I think you are saying the same - to go back to using that Pressure Release to remove as much air, correct?

                      Sorry, I just realized how wordy this is. :-)

                      Safe Travels & thanks again,
                      Grand Design-Imagine
                      2021 (1st Edition) 2600RB

                      Comment


                      • #12
                        Chipster 1st, I never drained the lines. I would turn the HWH on and wait 10-15 minutes then open one of the hot faucet valves for a second or so and relieve the spike in pressure. If you are trying to shave weight, look where your fresh tank is and how much water you are running in it. Reality is you are talking about 7-8 gallons of water (approx 1 cu ft) in the system. HWH accounts for most of this at 6 gallons. At 1 cubic ft of water that is under 65 lb. If its 2 cubic ft that's still less than 130 lb. Not worth the hassle of trying to drain the lines by crawling under the camper. You would be better off completely dumping all of the holding tanks and leaving the black tank empty till you get to the next stop.

                        I never opened the temp / pressure relief. Some here say its used to help control pressure rise in the system, but I can see that going both ways as increased temp of the trapped air causes increased pressure in the lines. I was always taught and heard that once the T&P valve was opened, it stood a good chance to start leaking.
                        Joseph
                        Tow
                        Vehicle: 2024 GMC K3500 Denali Ultimate Diesel
                        Coach: 303RLS Delivered March 5, 2021
                        South of Houston Texas

                        Comment


                        • #13
                          An RV water heater is designed to have a "dome" of air space at the top to absorb water expansion caused by heating the water. Over time, the air in this dome will be absorbed into the water. Without this expansion space, hydraulic water pressure will rise quickly until the pressure relief valve opens. This means that the pressure in your entire water system has reached 140 psi . (and you though it was at 50 psi because that's what your inlet pressure regulator is set at ) Heating very cold water would cause more expansion and could also be the reason that this air dome expansion space is being used up.

                          Water heater manufacturers provide information on how to re-establish an absorbed air space. But, if you are regularly draining the water heater, this should accomplish the same thing. As mentioned in several previous threads, the only way to know exactly what is going on is to install a system pressure gauge. Tee connected into any cold water line or even (temporarily) attached to the low point drain. The best $15 you will ever spend on understanding your RV water system.

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

                          Comment


                          • #14
                            The process to reestablish the air bubble is to turn the water source off. Open a faucet to relieve the system pressure. Open the water heater relief valve and drain water to create the air bubble. Let the relief valve handle snap closed. Let the water heater cool down so you don't get scalded before doing this.
                            Ted
                            2021 Reflection 310RLS
                            2020 F350 PS,CC,LB,SRW

                            Comment


                            • #15
                              Thank you, everyone. I think I under the 'bubble', and I think I understand how to establish it.
                              Again, thank you all.
                              Grand Design-Imagine
                              2021 (1st Edition) 2600RB

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