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No Hot Water Supply Woes and Repair T@B 400

RTWCTSRTWCTS Member Posts: 180
in Heating/Plumbing & Winterizing
On our last camping trip (uCamp) we had no hot water. Cold water would run through the spigots for about 10 seconds while set to hot and then stop, both on pump and city water. My first thought was the mixing valve. Before spending the money, I asked the Truma Service Rep during the first Alde session. He definitively said it couldn't be the mixing valve and that I must have the Nautilus valves set wrong.
I verified my valve setting at the site and looked in the Alde compartment. I noted the cold-water supply line to the pump was collapsed.


Reading through No Hot Water type discussions on the forum I learned of potential suction problems with cold supply check valve being installed backwards, etc. So, I assumed my collapsed line was the problem and waited until returning home to remedy things. At the house I had trouble breaking the crimp connectors on the PEX in the confined area, so I removed the assembly at the nearest screw on fittings, at the Nautilus and water pump.

With the crimp connectors and vinyl tube removed I made a new supply harness using PEX instead of the vinyl tubing. I had to trial fit several times and after it all 'dry fit' well enough I put most of the assembly together in the garage. I had to make one final connection in the T@B. All total I used two 90degree fittings and about 2feet of 1/2" PEX.

My cold-water supply through the pump is dramatically improved. It did not solve my hot-water supply issue though.
When disconnected at the mixing valve hot water flowed readily from the heater to the point where the push fitting connection enters the mixing valve. With nothing to lose, I decided to take apart the mixing valve to determine the problem. Behind the screen on the hot-water inlet side is a check valve. The screen was clear, but the valve didn't really move when gently prodded with a screwdriver. I disassembled the cold-water supply side, and the check valve moved freely. I went back to the hot-water check valve and exercised the valve, slowly increasing pressure with each push. Soon enough, it was functioning similar to the cold-water side check valve. 
Everything has been reassembled. The hot water is supply is functioning properly at all the spigots. I do not know the cause of the collapsed line or the stuck valve but am content since the system is nominal.
2023 TAB 400 Boondock
2025 Silverado (EV) or 2019 Colorado (ICE)
2018 T@B 320 Sold
Racing the Wind and Chasing the Sun
Virginia Beach, VA
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Comments

  • dsfdogsdsfdogs Member Posts: 631
    I'm pretty sure when I had the collapsed line it was because I'd forgotten to change the Nautilus to 'dry camping' prior to turning on the pump. Between using pliers and my fingers I was able to reform the hose to the round shape again without issue. 
    Debbie in Oregon
    Sold 2023 Tab 400
    Sold 2018 T@B 320S

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  • ventureboyventureboy Member Posts: 5

    This was very helpful.  I replaced the hose with pex like in this diagram. While I am not new to campers, I am new to the Tab 400.  This is a simple and rather ignorant question (I know) but I have water running out of the drain lines that are up under the camper.  Both of these lines have a toggle switch on the floor where all the hot water heater and piping is.  The water seems to run with the toggle in either position.  Am I missing something simple here.  Please say yes.


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  • pthomas745pthomas745 Administrator, Moderator Posts: 4,274
    Welcome to the Forums, and welcome to the Famous Yellow Flapper Valve club.  
    What year is your 400?
    The Yellow Valves are: drain valves for the two hot water tanks.  (You may only have one, depending on the year).  One of the Yellow Valves also works as a "pressure relief valve" for the plumbing.  If you are on city water, and did not use a water pressure regulator on the hose.....the Yellow Valve opens and releases the pressure, and water is dropped out of the drain.
    When the valve points up, it is open.  When it is "horizontal", it closes.  But: it can be pushed "below horizontal" and cause the valve to let water escape.  I'm sure you have played with the valves a bit, and you can just sort of feel when it pops into place by itself. Check to see if you have pressed it down too hard.  
    It is also possible for these valves to fail: they are spring loaded devices and eventually the spring will fade a bit.
    You also should check for exactly where the water is coming from under the trailer.  The Yellow Valve drains are directly below each valve, you can look underneath the trailer and see them.
    There are also low point drains for hot and cold water that need to be checked.  (The year of the trailer is important for this, too.)

    2017 Outback
    Towed by 2014 Touareg TDi
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  • ventureboyventureboy Member Posts: 5
    Thanks so much. I have a 2023. Yes I left these valves pushed down too far.  As I said I have replaced the crimped hose with pex. But I still don’t have any hot water. Acts just like it did before I replaced the flat hose. There has to be some easy answer here that I’m missing. Again. Thank you. 
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  • pthomas745pthomas745 Administrator, Moderator Posts: 4,274
    What happens when the valves are opened is the hot water tanks are drained.  The way to refill the hot water tank is to run a hot water faucet for a few minutes to refill the couple of gallons of water in that tank.  So, try that.
    Have you had hot water before? Do you have the Alde manual?  Is your Alde heat working?
    2017 Outback
    Towed by 2014 Touareg TDi
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  • ventureboyventureboy Member Posts: 5
    I believe the heat works. Testing everything before first trip this weekend. Could feel the tank was hot. And up front could tell the glycol was “bubbling”  Hot water was coming out underneath when I opened the flapper valve. I tried the hot water outside and inside. Nothing. Of course this was after wasting an hour to figure out my pressure regulator was stuck and had to use my backup. 😎. Any way No hot water on outside source or on pump. Maybe it’s the alde regulator. The red cap is very loose and turns very easily so it doesn’t seem connected to anything. 

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  • RTWCTSRTWCTS Member Posts: 180
    edited September 12
    @ventureboy
    The red cap on the mixing valve actually pulls off and is used to adjust the mix of hot to cold water. You'll see a triangle indent in the reed cap that fits the triangle of the adjustment knob when inverted. I would start there to see if that is the reason for no hot water.
    In my case the mixing valve itself was bad. The check valve on the hot water inlet was stuck, so no water was flowing. I was able to unstick the check valve as described in the last paragraphs of my original post. We just got back from a three-week road trip, and all is still functioning.
    2023 TAB 400 Boondock
    2025 Silverado (EV) or 2019 Colorado (ICE)
    2018 T@B 320 Sold
    Racing the Wind and Chasing the Sun
    Virginia Beach, VA
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  • ventureboyventureboy Member Posts: 5
    Thank you. I’ll pull the cap off as soon as I get home. And resume the effort there. 
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  • ventureboyventureboy Member Posts: 5
    I pulled off the red cap and used a 3/4” socket (same size as levelers) and opened it 1/4 turn. I now have water running from the hot side both inside and out.it must’ve been turned completely off for the hot water side. But hey, I wouldn’t have fixed the pex if I had found this right away.  Water and glycol both heating up. Now to check to see if the water actually gets hot. And whether I have to adjust the mix. You’ve helped so much. Thank you. Will update with final results. 
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