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Accumulator - Where do I install it?

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  • Accumulator - Where do I install it?

    Cate&Rob (and forum members),
    A small accumulator is on it's way.

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    I've been reviewing the plumbing configuration in my camper and can't quite wrap my head around where to install the device. I seem to remember something along the line of, "anywhere"...but my interpretation may be off.

    Why an accumulator? Because as noted in another thread and as shown in diagram #2 below, when the water heats up the gauge I installed shows the pressure in the water line skyrockets.

    Below is a rough sketch of how the system is effectively (not actually) configured in my 315RLTS.

    Diagram #1 represents an example of the gauge using city water with the water heater off and no accumulator in the system. Not an actual measurement on the gauge--just an example for contrast and comparison.

    Diagram #2 represents the results with the water heater on and no accumulator. Note the gauge is off-scale high. (It really does this!) The yellow highlighted double-lines show where the increased pressure is "felt" by the water system.

    Diagram #3 shows the expected results with the accumulator installed.

    Is there any reason to not install the accumulator under the kitchen sink on the cold water line? This is at the end of the water lines but it should, if I've got this figured correctly, still absorb the extra pressure in the lines due to the hot water expansion.

    Howard

    Edit: See update to diagram in post #14

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    Howard
    Last edited by howson; 04-08-2021, 06:04 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.

    Howard, 2017 Ford F-350 DRW, '19 315RLTSPlus

  • #2
    Welcome to the club! I put mine behind the wall in the basement (fifth wheel obviously) after the output of the nautilus. I think your logic Is sound, anywhere on the cold line should be fine.

    I looked for a picture of mine but couldn’t find one. I used a 2 gallon expansion tank from a big box store mounted to a couple large L brackets. I’m very happy, with the added benefit you can flush the toilet in the night without running the pump.
    Neil Citro
    2018 Reflection 28bh
    2019 F350 6.7L Long Bed Crew Cab

    Comment


    • #3
      I had one installed on my previous 5th wheel. It was on a platform that also contained the 12V water pump. It was on the output of the water pump so it would work with both city water and fresh water tank draw.

      My system was very similar to this one but cost much less ... https://www.amazon.com/Flojet-028401.../dp/B000O895KY

      Comment


      • #4
        howson
        Hi Howard,

        Think of the cold water line as a "manifold" with various inputs and outputs. The accumulator tank is just one of these (happens to be both an input and an output) and can go anywhere on the manifold.

        The accumulator that you have chosen will help to mitigate the pressure rise due to water heating, but will not provide the water reserve for things like toilet flushing, without the pump coming on. The tank is just not large enough.

        As Neilncitro and openrangeowners have noted, a larger tank will be cheaper and will accomplish more of the benefits you are expecting (at a cheaper price) . . . but you do have to find space for the larger tank. On the boat, I located one of these tanks up under a countertop where the space was not used by the shelf storage space of the cabinet below.

        You will often see these tanks oriented vertically and this goes back to when accumulator tanks did not have diaphragms and the air bubble had to be kept above the water. With a diaphragm separating the air from the water, the tank can be oriented in any direction.

        Rob
        Cate & Rob
        (with Border Collies Molly & Angel and their kitty Gracie)
        2015 Reflection 303RLS
        2014 Ecoboost F150 with Heavy Duty Payload Package
        Bayham, Ontario, Canada

        Comment


        • #5
          I need to purchase one of these. These will lose pressure over time like a tire where they need to be checked periodically. Recently found my well pump at home short cycling where the accumulator needed to be re-pressurized.

          Jim
          2017 Imagine 2600RB
          2015 GMC Sierra 4x4

          Comment


          • #6
            I am not down playing the reason for needing/wanting an accumulator/expansion tank but was surprised to see that your cold water lines also become pressurized when the water heater heats up. I thought the inlet to the water heater had a check valve to prevent back flow into the cold water supply line? Does your system not have this check valve?
            Attached Files
            Jeff and Debbie
            2021 Imagine 2250RK
            2015 Ram 2500 6.7 CTD Crew Cab Short Bed Factory Air-Ride Auto Level
            USMC Veteran

            Comment


            • #7
              The outlet of the water heater has the check valve, not the inlet.
              You can connect the accumulator anywhere on the cold water side of the system.
              Ted
              2021 Reflection 310RLS
              2020 F350 PS,CC,LB,SRW

              Comment


              • #8
                howson Howard, I would guess the statement "anywhere in the system" would mean that you can put it in any part of the plumbing cold water setup that is on the coach side of any check valves. The inlet to the HWH would be the most obvious line of choice as it is the best of all worlds. City and pump supply both share this portion of the system and water should flow freely in this area between the HWH and the faucets.
                Tow Vehicle: 2018 GMC K2500 Denali Diesel
                Coach: 303RLS Delivered March 5, 2021

                Comment


                • #9
                  Originally posted by Heavysledz View Post
                  I am not down playing the reason for needing/wanting an accumulator/expansion tank but was surprised to see that your cold water lines also become pressurized when the water heater heats up. I thought the inlet to the water heater had a check valve to prevent back flow into the cold water supply line? Does your system not have this check valve?
                  There is no check valve on the inlet to the water heater, so pressure rise in the water heater pushes back into the cold water feed line. There is a check valve on the outlet of the water heater, but its only purpose is to prevent back flow into the water heater when the bypass is opened . . . typically only a winterizing thing. Since this check valve is for back flow, it does not prevent out flow pressure from building in the hot water pipes as well.

                  There is an air space in the top of the water heater, intended to absorb the volume expansion when heating. This air dissolves into the water over time, removing the air cushion. This is why the pressure relief valve begins popping open and some water has to be drained from the water heater to re-establish this air space.

                  Rob
                  Cate & Rob
                  (with Border Collies Molly & Angel and their kitty Gracie)
                  2015 Reflection 303RLS
                  2014 Ecoboost F150 with Heavy Duty Payload Package
                  Bayham, Ontario, Canada

                  Comment


                  • #10
                    Originally posted by Heavysledz View Post
                    I am not down playing the reason for needing/wanting an accumulator/expansion tank but was surprised to see that your cold water lines also become pressurized when the water heater heats up. I thought the inlet to the water heater had a check valve to prevent back flow into the cold water supply line? Does your system not have this check valve?
                    Edit: Rob was typing at the same time I was!

                    TedS is right--the check valve is on the outlet, not the inlet. The reason it's there is to keep cold water from entering the water heater backwards when the cold water inlet is bypassed.

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                    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.

                    Howard, 2017 Ford F-350 DRW, '19 315RLTSPlus

                    Comment


                    • #11
                      Originally posted by MidwestCamper View Post
                      I need to purchase one of these. These will lose pressure over time like a tire where they need to be checked periodically. Recently found my well pump at home short cycling where the accumulator needed to be re-pressurized.

                      Jim
                      Hi Jim,

                      Pressure loss over time indicates problem . . . unless you have an older accumulator tank without a diaphragm separating the air from the water. In this case (or if there is a hole in the diaphragm) the air will slowly be absorbed into the water. Otherwise, the air in the top portion of the tank should not be able to get out. Soap testing around the schrader valve might be a good idea.

                      Rob
                      Cate & Rob
                      (with Border Collies Molly & Angel and their kitty Gracie)
                      2015 Reflection 303RLS
                      2014 Ecoboost F150 with Heavy Duty Payload Package
                      Bayham, Ontario, Canada

                      Comment


                      • #12
                        Howson,
                        in your schetches, the nautilus valve shown to the right of the water heater should be to the left. It directs water to either the water heater or water heater bypass. The check valve on the heater outlet prevents backflow when the water heater bypass is selected for winterization. The water heater out flow after the check valve joins the bypass flow so either can feed the hot water faucets.

                        You are correct in that pressure can rise quickly as water heats.
                        Ted
                        2021 Reflection 310RLS
                        2020 F350 PS,CC,LB,SRW

                        Comment


                        • #13
                          Originally posted by Cate&Rob View Post

                          Hi Jim,

                          Pressure loss over time indicates problem . . . unless you have an older accumulator tank without a diaphragm separating the air from the water. In this case (or if there is a hole in the diaphragm) the air will slowly be absorbed into the water. Otherwise, the air in the top portion of the tank should not be able to get out. Soap testing around the schrader valve might be a good idea.

                          Rob
                          Rob,

                          This may indicate a future problem but I figured the bladder would eventually lose some air pressure over time. I put this unit in about 12 years ago. I shut down the well pump, relieved pressure from the accumulator and aired it up to 2 psi below the low limit. So far its holding up but as you mentioned a small pin hole may indicate an impending issue. I did check the shrader with the ol spit test.

                          Jim
                          2017 Imagine 2600RB
                          2015 GMC Sierra 4x4

                          Comment


                          • #14
                            Originally posted by TedS View Post
                            Howson,
                            in your schetches, the nautilus valve shown to the right of the water heater should be to the left. It directs water to either the water heater or water heater bypass. The check valve on the heater outlet prevents backflow when the water heater bypass is selected for winterization. The water heater out flow after the check valve joins the bypass flow so either can feed the hot water faucets.

                            You are correct in that pressure can rise quickly as water heats.
                            Hmmm...I see that now. No water attempts to enter the water heater with the selector valve in bypass. Updated and posted below.

                            Thank you for the critique!

                            Howard


                            Click image for larger version

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Views:	56
Size:	121.5 KB
ID:	49780
                            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.

                            Howard, 2017 Ford F-350 DRW, '19 315RLTSPlus

                            Comment


                            • #15
                              TedSCate&Rob howson, I stand corrected...sorry for muddying the waters (no pun intended) with inaccurate information on my part.
                              Jeff and Debbie
                              2021 Imagine 2250RK
                              2015 Ram 2500 6.7 CTD Crew Cab Short Bed Factory Air-Ride Auto Level
                              USMC Veteran

                              Comment

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