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  • Fresh Water Tank Overflow - Revisited

    When we took our first trip in our Reflection 297RSTS four years ago, we ran into the issue were we were losing fresh water out of the overflow while traveling. It's hard to find fresh water at some of the places we go camping in the Arizona desert, so we usually fill up at home. On that first trip, I lost 2/3 or our water!

    In order to keep from losing a significant portion of our water while on the road, I installed a shut off valve on the overflow. This actually worked out well until our last trip. Here's the procedure that used to work well.

    1. Fill up the tank until water started to flow out of the overflow.
    2. Shut off the water supply, and close the valve on the overflow hose.
    3. Set up camp, turn on the pump, and set the Nautilus panel to "Dry Camping".
    4. Open the overflow valve and have the Mrs. run a faucet inside. This would typically break the suction and you'd hear air shooting up into the overflow.

    As soon as the air would start rushing, the water coming out of the overflow would stop and we'd camp as normal. BUT - On our last trip, this didn't work. When I attempted to run step #4 above, water kept flowing out of the over-flow and wouldn't stop. After it filled a five gallon bucket, I closed the valve. I'd open it from time to time as we were using water, and it always kept flowing. I couldn't hear any air going back up the overflow tube.

    I'm home now, and have time to fiddle with it. The tank was showing 2/3 full, but water was still flowing out of the overflow and you couldn't hear air entering. So I left the overflow open, and opened the tank drain. Amazingly, water was flowing out of both, and now air was entering. Finally, when the tank was about 1/3 full, I heard a huge rush of air, and finally water stopped flowing out of the overflow. I closed the tank drain and you could hear air being sucked into the drain tube for at least 60 seconds.

    This tells me that the tank is collapsing and no air can enter the tank until it finally gets low enough on water for the suction to stop. Next week, I'm planning on dropping the coroplast for some other work and I'll work on developing a method for proper tank venting if I can. In the mean time, I need to make sure to leave an air space at the top of the tank while filling.


    Click image for larger version  Name:	Water.jpg Views:	0 Size:	156.4 KB ID:	34619


    Jim
    Last edited by TucsonJim; 11-16-2020, 04:39 PM.
    Jim and Ginnie
    2024 Solitude 310GK
    GDRV Technical Forum Moderator
    GDRV Rally Support Coordinator

  • #2
    Jim

    I have had the valve on the overflow since new and have not had the issue that you are having. If you promise not to tell anyone I have on the last 2 occasions forgot to open the valve when using water from the fresh tank with the pump for a day , this results in the pump pulling a vacuum in the fresh tank , after I remember to open the valve on the overflow it sucks quite a bit of air in until the vacuum is released. I believe what you are experiencing may be do to elevation change or temperature change. Another thought might be these tanks a formed in such a way that there is no interior support this will allow the tank to possibly collapse when empty. When you are filling the tank the water will actually expand the tank to some point until water comes out of the over flow. Then when you close the overflow valve this will actually leave a little pressure in the tank , the tank wants to collapse to a rested state. When you travel to your destination , again with the altitude change or temperature change or both , you may gain some more pressure. Then when you open the over flow valve the "new" pressure in the tank wants to push the water out.

    Brian
    Brian & Michelle
    2018 Reflection 29RS
    2022 Chevy 3500HD

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    • #3
      Hi Jim,
      I have never had to do step 4. I stop filling the tank as soon as the overflow starts flowing and close the overflow valve right away. At camp I just open the overflow valve and have never had more than a small trickle come out for a few seconds. Like Brian, I have forgotten a few times to open the overflow valve for a while, when I open it then I hear air rushing in. I don't understand why you would have to always "break the suction". Could the overflow pipe inside the tank be at the wrong location? It doesn't seem like the tank would be flexible enough to collapse that much. I will be very interested in what you find out.

      Dave
      2016 Reflection 27RL
      2015 Silverado 2500HD 6L
      B&W Patriot 18k slider

      Comment


      • #4
        We're going to head out again this weekend for a short trip. The temperature and elevation will be very similar between the destination and home. I'll experiment a little more. But next week the fun begins with the underbelly clean up.

        Jim
        Jim and Ginnie
        2024 Solitude 310GK
        GDRV Technical Forum Moderator
        GDRV Rally Support Coordinator

        Comment


        • #5
          From basic physics, this should only occur when the overflow is below the level of the water in the tank. That would have to mean that either the overflow pipe was not installed at (or near) the top of the tank, but closer to either a mid-point or lower. The other option would be if the overflow pipe extends into the interior of the tank, and the entrance to the pipe, inside the tank, is below the interior water level. In order for water to siphon out of the tank, the entrance point for the water must be below the water level. Even if there were some sort of pressure inside the tank, either elevation or temperature change or the tank wanting to change shape, the only thing coming out of the tank should air, unless the pipe entrance is below the water line.

          I’ll also be interested to see what you find, as we have not had this issue but, we rarely travel with much more than 5-10 gallons of water in the fresh tank. My wife likes full-hoookups, so we just carry enough to use the bathroom, enroute. I also carry a spare 5 gallons in the bed of the truck.
          Tom and Janice (also known as Richter on the “Other” forum)

          First came the 18' Comfort bumper-pull, was great for 20 years.
          Now a 2019 Reflection 303RLS, second air, double glass, table and chairs
          2019 F350 Lariat 4x4 Crewcab with lots of goodies
          Andersen aluminum with the puck system holding it all together
          Cranberry Twp. PA, about 30 miles north of Pittsburgh

          Comment


          • #6
            TucsonJim
            Hi Jim,

            This is a really curious situation. As mentioned earlier by others, the the end of the blue overflow pipe inside the tank has to be getting below the water level. For water to come out both drain and overflow at the same time, air has to be getting in from somewhere else . . . or the tank is contracting/deflating. I wonder if tank deformation has been enough to somehow submerge the overflow pipe? It will be interesting to go through these fill/drain sequences when you have the coroplast removed and can observe what the tank is physically doing.

            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


            • #7
              Originally posted by Cate&Rob View Post
              TucsonJim
              Hi Jim,

              This is a really curious situation. As mentioned earlier by others, the the end of the blue overflow pipe inside the tank has to be getting below the water level. For water to come out both drain and overflow at the same time, air has to be getting in from somewhere else . . . or the tank is contracting/deflating. I wonder if tank deformation has been enough to somehow submerge the overflow pipe? It will be interesting to go through these fill/drain sequences when you have the coroplast removed and can observe what the tank is physically doing.

              Rob
              Rob - I'm sure it has to be the tank "deflating". It got down to about 1/3 of a tank before I heard it break the suction and there was a huge inrush of air through the overflow tube. I'm certainly going to see if I can recreate it while the liner is down. But in the mean time, I believe I need to be careful and leave an airspace at the top of the tank when filling up.

              Jim
              Jim and Ginnie
              2024 Solitude 310GK
              GDRV Technical Forum Moderator
              GDRV Rally Support Coordinator

              Comment


              • #8
                TucsonJim ,

                I know you know this info, but for the sake of others reading this thread your 297RSTS appears to have an Alpha VR295975WGR water tank, at least according to Grand Design's Parts Lookup website.

                Click image for larger version  Name:	Alpha with labels.JPG Views:	0 Size:	65.4 KB ID:	34650
                I agree that the tank must be collapsing as the siphon doesn't quickly reach equilibrium. When the pressure of the tank material trying to return to it's normal shape overcomes atmospheric pressure the siphon is broken. (I had to go watch a YouTube video to refresh my gray matter on how a siphon works.)



                So given the water tank wants to return to it's normal shape all it needs is a source of air to do so. So....that got me to thinking. Since my trailer is right out back, I did an experiment.

                What I did was fill the fresh water tank (valve open, of course). Water first started to drip out of the overflow with 45.6 gallons in the tank. At 49 gallons the water was flowing in a strong stream from the overflow.

                Click image for larger version  Name:	Out of overflow.JPG Views:	0 Size:	132.4 KB ID:	34651
                I turned off the water entering the tank and then the overflow valve to stop losing water from the tank. What I did then was remove the screen in front of the City Water intake valve and depressed the valve--and I could hear gurgling! When I reopened the overflow valve water continued to come out (as I'd overfilled the tank) but each time I closed the overflow valve and depressed the City Water valve I could hear air entering.

                After a couple of tries I removed water from the tank using the Dry Camping setting on the Nautilus. After removing pressure from the system I switched back to Powerfill and pressed the City Water valve--gurgling again. Repeat one more time and water stopped flowing from the overflow valve completely.

                Easier to see than read:



                The way to avoid the problem altogether is stop filling the water tank at 40 gallons. Then the problem of an overflow siphon won't happen.

                If the siphon does start, though, an easy way to stop it is using the City Water connection's valve to allow air to enter (with the settings on the Nautilus set to PowerFill).

                Here's my setup in case anyone's curious. (The red "V?" is a reminder to check the overflow valve and ensure it's open. I have a sticker at the Convenience Center pump switch, too.)

                Click image for larger version  Name:	V.JPG Views:	0 Size:	72.5 KB ID:	34652

                Let me know if it works for you!

                Howard
                Last edited by howson; 11-12-2020, 02:17 PM.
                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


                • #9
                  Brilliant solution Howard! Thanks much. Off to Amazon to purchase one of those fancy water gauges.

                  Jim
                  Jim and Ginnie
                  2024 Solitude 310GK
                  GDRV Technical Forum Moderator
                  GDRV Rally Support Coordinator

                  Comment


                  • #10
                    TucsonJim & Others. I have fought this issue from day one on my 28BH. I went through several permutations, I started with the valve on the overflow, it worked fine, but my memory did not. I attempted to move the valve rearward so I could access it easier with the slide out (for when I inevitably forgot to open it two days into camping) but that caused the described issue with water in the vent pipe not allowing air to flow. I solved this by using my Dewalt leaf blower to push the air into the tank so it could breath effectively, still not ideal. My next revision was the solution described in the other place with the vent run forward to the propane compartment, and a vacuum relief valve and a low point drain. I had limited results with this as well. I determined as mentioned above that the tank was simply too flexible to have enough suction to pull pretty much any water in the vent line back into the tank. Instead it was just "easier" for the tank to collapse on itself. I am sure I did not do this any favors by forgetting to open the valve. I dropped my coroplast looking for a solution, and actually removed my fresh tank. It was the flimsiest thing I had ever seen in my life. Even when full I could compress it by hand with very little effort. In my rig it was supported by steel straps underneath, and between each strap a belly formed with only a very small amount of water, which got worse as I added water. I shortened the straps hoping that might help, but it did not do much.

                    The vent line comes off the side of the tank towards the top as Howard shows, but it then immediately goes into two elbows to get it pointed down to the ground. What I finally did was remove the existing vent entirely, and run it at the top of the underside rearward. I then elbowed up and onto the back wall where I installed a roof vent (with a piece of screen inside to keep bugs out). Now it runs uphill from the tank all the way to the vent. I fill until water comes out, and when it stops as I use water gravity drains the water in the vent line back into the tank and it breaths normally. Not the most beautiful solution, but it works awesome and is totally automated. I have done three weeks in the rig with it, with no issues so far.

                    I will be back at the rig this afternoon and will take a photo of the vent on the back, but it pretty much looks as you would expect.
                    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.​

                    Neil Citro
                    2018 Reflection 28BH Pepwave
                    2019 F350 6.7L Long Bed Crew Cab

                    Comment


                    • #11
                      Originally posted by ncitro View Post
                      TucsonJim & Others. I have fought this issue from day one on my 28BH. I went through several permutations, I started with the valve on the overflow, it worked fine, but my memory did not. I attempted to move the valve rearward so I could access it easier with the slide out (for when I inevitably forgot to open it two days into camping) but that caused the described issue with water in the vent pipe not allowing air to flow. I solved this by using my Dewalt leaf blower to push the air into the tank so it could breath effectively, still not ideal. My next revision was the solution described in the other place with the vent run forward to the propane compartment, and a vacuum relief valve and a low point drain. I had limited results with this as well. I determined as mentioned above that the tank was simply too flexible to have enough suction to pull pretty much any water in the vent line back into the tank. Instead it was just "easier" for the tank to collapse on itself. I am sure I did not do this any favors by forgetting to open the valve. I dropped my coroplast looking for a solution, and actually removed my fresh tank. It was the flimsiest thing I had ever seen in my life. Even when full I could compress it by hand with very little effort. In my rig it was supported by steel straps underneath, and between each strap a belly formed with only a very small amount of water, which got worse as I added water. I shortened the straps hoping that might help, but it did not do much.

                      The vent line comes off the side of the tank towards the top as Howard shows, but it then immediately goes into two elbows to get it pointed down to the ground. What I finally did was remove the existing vent entirely, and run it at the top of the underside rearward. I then elbowed up and onto the back wall where I installed a roof vent (with a piece of screen inside to keep bugs out). Now it runs uphill from the tank all the way to the vent. I fill until water comes out, and when it stops as I use water gravity drains the water in the vent line back into the tank and it breaths normally. Not the most beautiful solution, but it works awesome and is totally automated. I have done three weeks in the rig with it, with no issues so far.

                      I will be back at the rig this afternoon and will take a photo of the vent on the back, but it pretty much looks as you would expect.
                      Thanks Neil. I'd really appreciate the photo.

                      Jim
                      Jim and Ginnie
                      2024 Solitude 310GK
                      GDRV Technical Forum Moderator
                      GDRV Rally Support Coordinator

                      Comment


                      • #12
                        Originally posted by TucsonJim View Post
                        Off to Amazon to purchase one of those fancy water gauges.
                        The regulars here know where I got the idea to use one of those "fancy" water gauges. Cate&Rob , of course.
                        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


                        • #13
                          Not a dry camper so really don't travel with tanks full. We are full timers and do have to use tanks in freezing and below temperatures so have some experience with filling them.

                          Reading through the threads it looks like the valves added to the end of the overflow valves are being closed while water is still running out of them and (reading between the lines) the water supply is still on. My question is that if the water supply is shut off when water starts flowing out of the overflow, and the valve on the overflow is left open until water stops flowing out the overflow, would this not provide the air cushion needed to prevent siphoning? There may be some water in the the overflow line from sloshing when the valve is opened again, but that should be minimal and there should not be any siphon effect.
                          John
                          2018 Momentum 395M
                          2018 Ram 3500 Dually
                          Every day is a Saturday, but with no lawn to mow.

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                          • #14
                            Originally posted by howson View Post

                            The regulars here know where I got the idea to use one of those "fancy" water gauges. Cate&Rob , of course.
                            X2 ! - And my 54 gallon fresh tank took nearly 54 before the overflow started dripping. As our grandson would say, "that makes my tummy happy !"


                            Dan
                            Dan & Carol
                            2014 303RLS Reflection #185 (10/2013 build)
                            2012 Silverado LTZ Crew Duramax 2500HD - 2700/16K Pullrite Superglide

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                            • #15
                              Jim TucsonJim - thinking outside the technical box......and this is a stretch, of course knowing your focus on accuracy, I thought about something that happened to us this summer.

                              We have never had issues with our fresh tank loosing much water after filling.....maybe a gallon or so at most and that is rare. However, we camped in a different area of our "go to" campground this summer, and as I was backing in and stopped at the back of the site, I saw a trailer of water on the paved road and all the way into the gravel site. I thought "what ?"......this has never happened before. The water just kept running out of the overflow. I pulled forward and backed in again a couple more times to get more level side to side (I thought I was level the first time) and the water was still coming out.

                              So I checked the level and found we were tilted much more to the street side that usual even though I thought we looked gtg. I moved over to where I thought level and the water stopped flowing. Knowing that the fresh tank design/placement along with the over lfow configuration would allow for water to probably flow from the tank, I learned that a pretty good tilt downward on the street side caused this situation.
                              Now, all this said, I am sure you were precisely level using some top secret missel guidance technology so my story is probably not relevant to your scenario. However, at times, it never hurts to go out on a limb just in case.

                              Please keep us posted on your ultimate findings.......I am quite curious.

                              Dan
                              Dan & Carol
                              2014 303RLS Reflection #185 (10/2013 build)
                              2012 Silverado LTZ Crew Duramax 2500HD - 2700/16K Pullrite Superglide

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