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  1. #21
    Site Sponsor Cate&Rob's Avatar
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    Hi Nick,

    It would be interesting to know what alloy the water heater tank is made of . . . since the manufacturer does not include a replaceable anode which would be the normal way of protecting against galvanic corrosion if that were expected to be a problem. I might be able to make the spacer that I fabricated between the tank and the valve, from a plastic part. This would electrically isolate the brass valve from the aluminum? tank. Something I will have a look at. Thanks for the "observation".

    Rob
    Cate & Rob
    2015 Reflection 303RLS

  2. #22
    Seasoned Camper
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    Quote Originally Posted by Cate&Rob View Post
    Hi Nick,

    It would be interesting to know what alloy the water heater tank is made of . . . since the manufacturer does not include a replaceable anode which would be the normal way of protecting against galvanic corrosion if that were expected to be a problem. I might be able to make the spacer that I fabricated between the tank and the valve, from a plastic part. This would electrically isolate the brass valve from the aluminum? tank. Something I will have a look at. Thanks for the "observation".

    Rob
    This is according to http://www.rvwaterheater.net/

    Atwood & Suburban water heaters are corrosion resistant but they address this issue differently. Atwood puts cladded Aluminum to good use. Not only does it make for a much lighter water heater, in fact up to 14-30 lbs lighter making them the lightest in the industry, it helps to combat corroding effects simply due to its construction. So, there is no need for anode rods.

    Suburban water heaters, although bulky, make up for being hefty by being fully equipped to ward off corrosion by utilizing porcelain lined steel tanks and electrolytical action "absorbing" anode rods. Their method is so effective, if maintained properly, it can double or even triple the included 3 year limited warranty.

    Brent
    Brent & Gina
    2018 Ford F250 PSD Crew Cab
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  3. #23
    Rolling Along
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    I'll just post this and people can decide for themselves on the corrosion issue.

    https://www.fastenal.com/web/en/70/corrosion

    Our last 5th wheel had an Atwood heater with nylon plugs. In twelve years I never had one actually break but did have one start to leak on a trip. That's why I carry a spare. Maybe they made better plugs then but I figure if I ever have a nylon plug leave some of its threads in the heater, what I can't pick out, I will be able to chase out with a pipe thread tap. If a brass fitting freezes in there, I am hooped so the potential downside of using a brass plug just isn't worth it to me.
    Nick and Nancy
    Abbotsford BC
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  4. #24
    Site Sponsor Cate&Rob's Avatar
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    Water Heater Drain Plug 2.0

    Thanks for all the info that you guys dug up on this topic.

    The interior of the Atwood tank might be coated, but the threaded drain plug opening looks to be raw aluminum. Thus, probably the reason that they use a plastic rather than a brass plug. Galvanic potential between brass and aluminum in contact with each other and in water, means that the aluminum anode will corrode. The brass cathode will not. The solution for this is to electrically isolate one from the other.

    Thus . . . still the brass thumb screw drain valve, but the part that threads into the hot water tank is now plastic.
    Took a little more custom machining of the brass valve to adapt it to this plastic piece . . . but this combination of parts should work.

    Click image for larger version. 

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    Rob
    Cate & Rob
    2015 Reflection 303RLS

  5. #25
    Long Hauler howson's Avatar
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    Quote Originally Posted by Cate&Rob View Post
    Water Heater Drain Plug 2.0

    Thanks for all the info that you guys dug up on this topic.

    The interior of the Atwood tank might be coated, but the threaded drain plug opening looks to be raw aluminum. Thus, probably the reason that they use a plastic rather than a brass plug. Galvanic potential between brass and aluminum in contact with each other and in water, means that the aluminum anode will corrode. The brass cathode will not. The solution for this is to electrically isolate one from the other.

    Thus . . . still the brass thumb screw drain valve, but the part that threads into the hot water tank is now plastic.
    Took a little more custom machining of the brass valve to adapt it to this plastic piece . . . but this combination of parts should work.

    Click image for larger version. 

Name:	image.jpg 
Views:	150 
Size:	100.2 KB 
ID:	1838

    Rob
    Very old thread...so are you still using this setup or have something better? If the same as shown in the pic, was it a custom installation or just putting together parts from off the shelf at Lowes or Home Depot?

    The salesman at Camping World tried to sell me the brass CAMCO drain and I told him about the galvanic corrosion potential. He looked at me like I was odd (well, that's actually true) and said he'd never heard of the issue.
    2017 Ford F-350 DRW 6.7L Platinum
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  6. #26
    Site Sponsor Cate&Rob's Avatar
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    Quote Originally Posted by howson View Post
    Very old thread...so are you still using this setup or have something better? If the same as shown in the pic, was it a custom installation or just putting together parts from off the shelf at Lowes or Home Depot?

    The salesman at Camping World tried to sell me the brass CAMCO drain and I told him about the galvanic corrosion potential. He looked at me like I was odd (well, that's actually true) and said he'd never heard of the issue.
    Hi Howard,

    That drain plug is still in place and still working just fine. No corrosion between the plastic piece and the aluminum that it threads into. Interesting that you should mention this because I was just showing this to a neighbour with a different RV brand, but the same water heater. He is off to find parts to make something similar for his water heater.

    The key to making one of these is finding a plastic bushing with a 3/4" MPT on the outside and a 1/2" FPT on the inside. The important thing is that there is plastic between the aluminum and the brass. From there, you can use standard brass 1/2" PT components to bring the drain petcock out to where it will be just inside the cover, but still drain on the ground.

    Finding a CW salesman who didn't understand galvanic corrosion, is probably not a big surprise .

    Rob
    Cate & Rob
    2015 Reflection 303RLS

  7. #27
    Long Hauler howson's Avatar
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    Quote Originally Posted by Cate&Rob View Post
    The key to making one of these is finding a plastic bushing with a 3/4" MPT on the outside and a 1/2" FPT on the inside.
    Since I'm relatively ignorant when it comes to plumbing I had to do some research.

    The most widely used pipe threads in North America are NPT (National Pipe Taper). Some confusion may result from the use of NPT, FPT, and MPT in describing threads. Both FPT and MPT are NPT threads, with FPT meaning female threads (internal) and MPT meaning male threads (external). Stolen from https://www.pooleyinc.com/pdf/PipeThreads.pdf
    2017 Ford F-350 DRW 6.7L Platinum
    2019 315RLTS (purchased 16 Jul 18 from Campers Inn RV in Byron, GA)

  8. #28
    Site Sponsor Cate&Rob's Avatar
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    Quote Originally Posted by howson View Post
    Since I'm relatively ignorant when it comes to plumbing I had to do some research.

    The most widely used pipe threads in North America are NPT (National Pipe Taper). Some confusion may result from the use of NPT, FPT, and MPT in describing threads. Both FPT and MPT are NPT threads, with FPT meaning female threads (internal) and MPT meaning male threads (external). Stolen from https://www.pooleyinc.com/pdf/PipeThreads.pdf
    Hey Howard - You've got it figured out! The bushing that you need in plastic or PVC, to electrically isolate the aluminum from the brass, is shown in the attached picture.

    Rob
    Attached Thumbnails Attached Thumbnails schedule-40-pvc-reducer-bushing-mpt-fpt_5.jpg  
    Cate & Rob
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  9. #29
    Rolling Along kevinpo's Avatar
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    Hello,
    A nylon reducer bushing would be preferred IMO.

    Regards,
    Kevin
    2015 Ram Laramie 3500 4x4 LB Dually Crew Cab
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