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Water siphon discussed ad nauseum. No info direct from Grand design?

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  • #16
    Originally posted by Jlawles2 View Post
    Guest Jim, Why not take one of the high point vacuum breakers (vented loop) like in the other post and just route the line back to where it came from? Put one of the AAV vents on the top of the breaker. https://www.homedepot.com/p/STUDOR-R...0353/203111264 is a one way valve. Lets air in but not air or water back out.

    https://www.amazon.com/Five-Oceans-O...86078675&psc=1

    It looks like they have the AAV built into the top of a few of them.
    I believe this would also be a good solution as well as several others on the forum. Like Dave, I've had campers with a traditional vent that worked well. With the locking gravity fill, the vent is protected from direction contact from rain and road debris. Also a full tank cannot slosh where we travel with a full tank and near empty when returning home. With this simple design, the vent will prevent tank collapse and allow for expansion. If the vent allows for efficient water flow from the pump, I will leave the overflow valve closed and use it only for filling the tank.

    Jim

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    • #17
      I think that you guys are making this too complicated. Based on all the observations and discussion in the previous thread https://gdrvowners.com/forum/operati...ter-tank/page5 what is necessary is to break the siphon column of water in the vertical vent/drain tube which is capable of sufficient vacuum to collapse the tank, lifting the water up to the vent connection and continuing the water flow by siphon action. The air to do this does not have to come from above the tank. Grand Design is going to test the parallel down tube theory that I proposed on 2/27 in post 62 of that thread . . . and advise on whether this solves the problem.

      Another potential solution would be to run the vent line down at a very shallow angle (rather than vertical) so that air could pass above a partially full flow of water, which would also break the vacuum at the tank connection.

      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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      • #18
        Originally posted by Cate&Rob View Post
        I think that you guys are making this too complicated. Based on all the observations and discussion in the previous thread https://gdrvowners.com/forum/operati...ter-tank/page5 what is necessary is to break the siphon column of water in the vertical vent/drain tube which is capable of sufficient vacuum to collapse the tank, lifting the water up to the vent connection and continuing the water flow by siphon action. The air to do this does not have to come from above the tank. Grand Design is going to test the parallel down tube theory that I proposed on 2/27 in post 62 of that thread . . . and advise on whether this solves the problem.

        Another potential solution would be to run the vent line down at a very shallow angle (rather than vertical) so that air could pass above a partially full flow of water, which would also break the vacuum at the tank connection.

        Rob
        Rob,

        I've not seen a siphon issue on my tank but just slosh while traveling. The 5ft piece of hosed routed up through the floor and mounted to the underside of the countertop and back down to a protected gravity fill vent is simple enough. All GDRV needs to do is add a vented gravity fill to solve their issues IMO. A baffled tank would be beneficial as well.

        Jim
        Last edited by Guest; 03-27-2021, 07:51 AM.

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        • #19
          Originally posted by MidwestCamper View Post

          Rob,

          I've not seen a siphon issue on my tank but just slosh while traveling. The 5ft piece of hosed routed up through the floor and mounted to the underside of the countertop and back down to a protected gravity fill vent is simple enough. All GDRV needs to do is add a vented gravity fill to solve their issues IMO.

          Jim
          Hi Jim,

          Agreed that a vented gravity fill will solve the problem. I'm not sure that Grand Design will see adding this feature to all Reflections, Solitudes and Momentums as an easy (or inexpensive) thing to do. Many owners (including me) never travel with anything more than a few gallons in the water tank . . . so, have never experienced this problem.

          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


          • #20
            Originally posted by Cate&Rob View Post

            Hi Jim,

            Agreed that a vented gravity fill will solve the problem. I'm not sure that Grand Design will see adding this feature to all Reflections, Solitudes and Momentums as an easy (or inexpensive) thing to do. Many owners (including me) never travel with anything more than a few gallons in the water tank . . . so, have never experienced this problem.

            Rob
            Rob,

            Understand. Many folks that want to boondock are requesting a gravity fill. I'm fortunate to have one on my Imagine even though its at a much lower price point. I also do not overfill the tank but shut off the water hose as soon as I see water coming from the overflow. This may make a difference to prevent the suction issue with tank collapse. A baffled tank would prevent tank collapse as well as slosh.

            Here is a better example of a baffled tank. Blow molded with integrated baffles.

            https://www.tek-tanks.com/product/25...-baffled-tank/

            Jim
            Last edited by Guest; 03-27-2021, 09:05 AM.

            Comment


            • #21
              HI all. The vented fresh fill without the other overfill system would be the simple way to go and believe where I am headed. I do not think the blue overfill/vent is needed in the first place. We had a class "A" that was a real problem with the tank tube overfill. It did have a third vent routed into a bin of all things once I put valves on the overfill I had no more problems. If the exterior hole for the fresh fill is too smallon our 2600RB for the combo fill/vent would there be much issue making the wall hole larger?

              Dave
              flyfshrockies, 2021 imagine 2600RB, Ford F-150, XLT supper crew 3.5 eco boost with max tow. Dave and Toni (and the awesome Aussie Bayley, he's the social one)

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              • #22
                Originally posted by flyfshrockies View Post
                HI all. The vented fresh fill without the other overfill system would be the simple way to go and believe where I am headed. I do not think the blue overfill/vent is needed in the first place. We had a class "A" that was a real problem with the tank tube overfill. It did have a third vent routed into a bin of all things once I put valves on the overfill I had no more problems. If the exterior hole for the fresh fill is too smallon our 2600RB for the combo fill/vent would there be much issue making the wall hole larger?

                Dave
                Dave,

                A through the wall vent would be fine as long as it prevents moisture from the road, rain or dirt from entering the vent. A secondary AAV that some of the folks are showing could help which could be mounted inside. I'm keeping the overflow with the valve and will test with the valve closed to see if the gravity fill vent is adequate. This can also be calculated if the temperature of the water and flow from the pump in known. I'll take the easy route and just listen at the vent. If the pump is ran at full flow and shut down, airflow at the vent should stop at or close to the water pump turning off. If there is a significant vacuum on the tank, I'll need to be sure to open the overflow valve. I believe the vent will handle the outgoing water flow.

                Also the overflow is used to prevent over pressurization of the tank when filling. The smaller vent hose would most likely not be capable of preventing over pressuring of the tank since water would be passing though the vent if the tank is overfilled.

                Jim
                Last edited by Guest; 03-27-2021, 10:45 AM.

                Comment


                • #23
                  Guest Lots of good thoughts on this. I would think that the vent will handle the volume of water/air extraction from the pump at maybe 2.5 gallons per minute that the pump flows, that should be at most about a 1/3 of a cubic foot of volume per minute. Let us know how this project proceeds, lots of people with this water concern. BTW the old style combo vent/filler never seemed to intake dust, dirt, rain etc. but then again how would a person know?

                  Dave
                  flyfshrockies, 2021 imagine 2600RB, Ford F-150, XLT supper crew 3.5 eco boost with max tow. Dave and Toni (and the awesome Aussie Bayley, he's the social one)

                  Comment


                  • #24
                    Originally posted by RobWNY View Post
                    I'm interested to learn more about this issue as well. Your tank will be empty in no time with that much water flow! When you heard not to overfill the tank, did they give a suggestion on how much water in the tank would they consider to be "over filled"
                    This is the factory response, "The instructions I would like to give to you on this is when you fill your tanks fill them till the monitor panel shows they are full. If you fill them till water comes out the over fill tube that will cause the tanks to balloon at a little and when that happens it will cause the water to start to out the overfill tubes and will cause it to siphon out even after has set if those tanks are over fill once you move the unit it can cause the tank to force the water out the over flow tubes".

                    Comment


                    • #25
                      Originally posted by TedS View Post
                      Please you post the factory service note here. Curious minds want to know.
                      I'm going to search for it again. It was on one of the 4 GD Facebook pages I follow. Unfortunately I didn't save the image. It was directions for putting loops in the vent lines as high as a tech could get them.

                      Comment


                      • #26
                        Originally posted by Dan P View Post

                        This is the factory response, "The instructions I would like to give to you on this is when you fill your tanks fill them till the monitor panel shows they are full. If you fill them till water comes out the over fill tube that will cause the tanks to balloon at a little and when that happens it will cause the water to start to out the overfill tubes and will cause it to siphon out even after has set if those tanks are over fill once you move the unit it can cause the tank to force the water out the over flow tubes".
                        Good advice. With my Imagine having the gravity fill there is a small volume of air in the fill tube that I believe acts as a buffer since I've not seen this on my rig. However, I also fill to where I just begin to see a trickle out of the overflow.

                        Jim



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                        • #27
                          Originally posted by flyfshrockies View Post
                          Guest Lots of good thoughts on this. I would think that the vent will handle the volume of water/air extraction from the pump at maybe 2.5 gallons per minute that the pump flows, that should be at most about a 1/3 of a cubic foot of volume per minute. Let us know how this project proceeds, lots of people with this water concern. BTW the old style combo vent/filler never seemed to intake dust, dirt, rain etc. but then again how would a person know?

                          Dave
                          Dave,

                          Agree. I also would not have known how much debris was entering the vent on my last rig. I already have the locking gravity fill where the vent sits protected behind the cap so it may help to prevent debris from entering the tank. These vents have been used for decades where all I can figure is the overflow was installed to prevent over pressurizing the tank. Not thought out too well without a baffled tank.

                          Weather is warming but we always get a snow storm in April so I need to hold off a bit before removing the cover.

                          Jim
                          Last edited by Guest; 03-27-2021, 11:46 AM.

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                          • #28
                            There is also a lockable hatch version of a gravity fill port.
                            Attached Files
                            Ted
                            2021 Reflection 310RLS
                            2020 F350 PS,CC,LB,SRW

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