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  1. #1
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    Dometic 2021 Hot Water Heater Drain Cap Mod.

    The new Dometic hot water heaters have a confounded drain CAP, not a plug like the old ones. Mine was dripping with just water in the tank, once it was heater, it forced water past it. When I took it off to drain the water heater, it was deformed from the heat.

    Anyhow, the first picture is of the confounded cap. The following ones are the 1/4 turn brass valve I put on it. I bought the valve at Lowes.

    The drain pipe is aluminum, and I'm aware the aluminum and brass have a metallurgic reaction to one another. PVC wasn't an option due to the heat. So, I wrapped the drain pipe with a ton of teflon tape, then put plumbers pipe dope on that, the screwed the drain on.

    I did have to remove the manifold to get it on, so there is that.

    The blue did on the drain plug is the pipe dope. It didn't work.Click image for larger version. 

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    Mark & Mary. Full-timing across the USA (and Canada)!
    Current Coach: 2021 Grand Design Reflection 320MKS
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  2. #2
    Setting Up Camp
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    No zinc anode in the drain point?
    2018 Chev Silverado 3500 HD diesel
    2021 Solitude 380FL

  3. #3
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    Quote Originally Posted by Max Owner View Post
    No zinc anode in the drain point?
    Nope. Not even a mention of one in the manual either.

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    Mark & Mary. Full-timing across the USA (and Canada)!
    Current Coach: 2021 Grand Design Reflection 320MKS
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  4. #4
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    I couldnít find a compact ball valve like yours at Menards so the one below is on its way from Amazon. I might be able to remove the handle to install it. Itís brass like yours, but plated. Iím not too concerned with dissimilar metals on the outside of the unit (metallurgist here btw). The lack of an anode is a bigger deal long term, but thatís just the way it is.

    Click image for larger version. 

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  5. #5
    Fireside Member BC315RLTS's Avatar
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    Quote Originally Posted by Max Owner View Post
    No zinc anode in the drain point?
    Dometic/Atwood water heaters have an aluminum tank so no need for the anode rod.
    2019 Reflection 315RLTS
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  6. #6
    Setting Up Camp
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    All my trailers have had the anode. Never paid much attention to the brand of them to know any better.
    2018 Chev Silverado 3500 HD diesel
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  7. #7
    Site Sponsor Petrovsky's Avatar
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    I too have the same issue with the original plug. Received new TT, tested water system, slight leak. Tightened and started water heater. No leak when hot. Today noticed that plug was leaking. No teflon on plug. Tightened again but it still leaks under pressure no heat. Dealer has no replacement plugs at the current time (WOW!). However he offered a solution, an endcap. I will try this tomorrow as the inside has a flare. The cap is a harder material than the original Dometic cap so hopefully it will do the trick. Have to sanitize system anyways.

    I like the idea of a ball valve but am concerned about galvanic corrosion on the Al threads. Not the brass. Teflon tape should help mitigate but not eliminate. If the brass on aluminum was always cold, less of an issue. But kinetics dictate an increase in reaction rate as the temperature of the two materials rises.

    I wonder if Seaway has something that can be used on the hot side?
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  8. #8
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    Quote Originally Posted by Petrovsky View Post
    I like the idea of a ball valve but am concerned about galvanic corrosion on the Al threads. Not the brass. Teflon tape should help mitigate but not eliminate. If the brass on aluminum was always cold, less of an issue. But kinetics dictate an increase in reaction rate as the temperature of the two materials rises.

    I wonder if Seaway has something that can be used on the hot side?
    I did both Teflon tape and plumbers pipe dope (snot, or whatever you want to call it). I know it won't stop the galvanic corrosion, but it was what I had to work with in such a short time. I just think it's crappy that Dometic went to a cap instead of a plug. I thought about an aluminum cap, but then I thought about having to remove it; I said the heck with the metallurgic reaction, and just did the brass 1/4 turn valve. I'll pay for it later, but we are actually thinking about putting in a tankless water heater. (Maybe... The wife is waffling on it still... Okay, I'M waffling on it still!)

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  9. #9
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    I think this is the product number for the drain CAP. Dometic 92102 Drain Cap Service Kit. Found it for sale at Walmart.com and Boat & RV Accessories, but not on Amazon. Ordered one today; we'll see if it fits when it arrives. Nice to have spares.
    92102 Drain Cap Service Kit by Dometic. Dometic's Drain Cap Service Kit(x2) is compatible with Gas/Electric 6 Gallon Water Heaters.

  10. #10
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    I put an o-ring in the cap and it has been working well.

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