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Thread: Smallest allowable tank size?

  1. #16
    Nuclear Engineer nukeman's Avatar
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    Yes. Electric WHs will use only one element at a time. With a 30A breaker, you could run a 40, 50, etc. gallon heater (assuming you had the space and support). Most of the larger WHs have 4500W elements and some have 5400W elements.

    However, a 30A circuit normally protects a 10ga wire. Normally, you have a 20A breaker protecting a 12ga wire. I do know that mobile homes do not always follow the same codes as stick-built, but not sure offhand where the electric codes fall under that.

    With 3500W elements, you should be pulling about 15A, so the 12ga wire is okay from that point of view, but the 30A breaker still may not be correct.

    Maybe with some pictures of the structure under the WH, we might be able to come up with some way to better support it.

  2. #17
    DIY Senior Member guy48065's Avatar
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    I'm in agreement with ImOld on this one. Water heaters haven't changed much in the 40 years since your MH was built--it was designed to handle the weight back then, so what does it need to meet the challenge today?
    Is the space the heater inhabits only supported by one cantilevered outrigger or will adding a new layer of 3/4 ply span 2 outriggers? Is the HWH located in its original spot or has it been moved? Having the wire come through a hole punched in the wall sure doesn't sound original-spec to me.
    Romeo and Atlanta, MI

  3. #18
    DIY Member ImOld's Avatar
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    Let's try again!

    The water heater is in the normal area, rear closet, for that type of mobile home.

    It is designed to be there.

    The fact that DIY's have screwed things up over the decades doesn't change that fact.

    I removed all the bad stuff, including an absolute maze of plumbing and wiring from a 3'X3' floor area.

    I then sister-ed floor joist material onto the good stuff.

    I then covered the area with 3/4" plywood and on top of that 1/2"of hardi cement board.

    At no time did I feel a need to add any support to the ground although you could with cement blocks and shims, just as the frame is being supported.

    This is the 12 year old, 30 gal water heater, that was removed and re-installed after the floor repair.

    Works as new.

    I love pictures.
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  4. #19
    DIY Senior Member kcodyjr's Avatar
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    I don't believe the WH has been moved on the basis of a whole bunch of old crappy corroded copper tubing that converged on that spot in parallel with the newly poorly installed pex. I do believe the original heater was smaller though; there's supposed to be a linen closet above the space starting at 34" above the floor, which had been sloppily gutted to make room for a taller heater. Also, the idiot had taken a sawzall to the master bedroom closet wall to make the access opening taller.

    I should clarify, the underbody outriggers aren't cantilevered; they're welded to the I-beam, 9" in height there, and extend 32", about 2" short of the edge of the trailer. The spacing changes; there's one near the forward edge of the heater location, next one forward 3', next one back 4', but the measurements were imprecise. If I were to guess, either the spacing is in metric units, or the workmanship well and truly blows like nothing has ever blown in the history of workmanship, or blowing.

    Above that is a layer of some kind of board; thin, weak, and seemingly asphalt coated, or similar. Above that is a thin layer of factory fiberglass and a poly vapor barrier. Hey, wait a minute - that means the subfloor cavity is supposed to dry inward, which it won't in a bathroom. Duh, there's why a seeping tub turned into a big rot problem. Looks like I'm ripping out as much of that poly as I can see.

    Above that are the 2x4's on their side in the transverse direction. Those are the ones that cantilever weight. They're spaced 4' on center and don't quite line up with the outriggers below.

    Above that are irregularly spaced longitudinal 2x6 joists, notched where they ride over the transverse 2x4's, including a single thickness "rim joist" that doubles as a sill-in-midair.

    Next the factory put down 3/4" particle board subflooring, then 1/4" of finish flooring edge to edge, and then started building exterior, then interior walls. Yeah, stupid. Much of that has been ripped out and replaced already, and from what I've seen, without much regard to the fact that it's supposed to be holding the walls up.

    My first thought to handle the weight was to cantilever inward using some 3/4" hardwood ply, but it would mean tearing up the vanity, the partition separating the bathroom from the master bedroom, the toilet, and a few layers of flooring.

    My next thought is that I could expose more subfloor cavity about 2.5' sternward into the MBR closet, to reach the next transverse 2x4. The next one forward is under the tub and already exposed, but already subject to significant loading by the tub. Unfortunately, the next one forward of that is under my kitchen. There's an accessible void there, which stops 9" short of where that 2x4 would be. I'd think two extra 12' joists, spanning a total of four transverse 2x4's, just might do the job.

    I'll see what I can do about getting some pictures.
    Last edited by kcodyjr; 11-19-2013 at 10:20 AM. Reason: Feet, not inches...

  5. #20
    DIY Senior Member kcodyjr's Avatar
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    That looks a good bit shorter than the one I have, and doesn't look any wider. Stanley McTape says mine is 45" high and 18" in diameter. If that wall plate is at the standard height for a lightswitch, mine would be blocking the view of it.

    Agreed that it's the location it's supposed to be, but it isn't the heater that's supposed to be there. It's definitely bigger than original, and neither the manual nor the tank says anything about being UL approved for mobile homes.

  6. #21
    DIY Member ImOld's Avatar
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    That is the same size as my water heater

    Here's a before and after of the bedroom where the water heater is located.

    Floors not done yet.

    If I can do it so can you.

    I almost want to stay here but I'm doing the remodel for a friend and then back I go to Arizona.
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  7. #22
    DIY Senior Member kcodyjr's Avatar
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    I'm a little confused by those pics; it looks like the spot where I thought the WH would be, used to be built-in drawers. Is the WH closet off to the left? Am I looking at the stern wall of the trailer or is that an interior partition? The hallway would also be to the camera's left?

  8. #23
    DIY Senior Member kcodyjr's Avatar
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    Default Pics of the area.

    Sorry for two of the pics being on their sides, and for all the nails and debris and crap. The housekeeping staff are spending a year dead for tax reasons. The new plywood you're seeing is simply resting atop the cheap factory underskin to keep the critters and cold air from coming in.

    The WH cavity. The heater is standing in the MBR closet.
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    The middle area where the tub goes. WH to the left, kitchen to the right.
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    The partition to the kitchen.
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  9. #24
    DIY Member ImOld's Avatar
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    Way too much talk and not enough action.

    It is what it is.

    You seem to be hung up on where's and why's.

    My allotted budget and time frame precluded me from "rearranging" anything.

    I certainly hope there will be insulation in those exterior walls.

    I suggest you find a mobile home forum where you will realize your predicament is commonplace.

    I'm done here.

  10. #25
    DIY Senior Member kcodyjr's Avatar
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    Thanks for your thoughts, ImOld.

    I avoided the MH forums on the basis that MH DIY screwups must be getting their advice there.

    Yes, there will be insulation; I'm thinking a 1 7/8" sheet of polyisocyanurate. Fiberglass sucks at 2x3 depth anyway, plus this thing eats up the outer half-inch with furring and wiring.

  11. #26
    DIY Senior Member guy48065's Avatar
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    Just a datapoint to your original question. My cottage has a 20 gal electric HWH about the size of an end table. It looks puny. I am surprised though that I can take a normal-length normal-temp shower. It is in a vented crawlspace in northern Michigan and doesn't have a blanket. IOW--far from ideal environment but It works. I would certainly recommend that over "army showers".
    Romeo and Atlanta, MI

  12. #27
    DIY Senior Member Reach4's Avatar
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    Quote Originally Posted by guy48065 View Post
    I would certainly recommend that over "army showers".
    I think it the Navy showers that save the most water.

  13. #28
    Retired Defense Industry Engineer jadnashua's Avatar
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    First, change the breaker to a 20A one, and then, at least, it will protect the 12g wire properly - 20A is fine for that WH.

    Second, if you can't bridge proper supports for the new subfloor you need, you need to come up with some way to transfer that load to the ground. How you do that is not that easy to tell without being there.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  14. #29
    DIY Senior Member kcodyjr's Avatar
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    No argument on the breaker. That'll take me 5 minutes including moving my stuff out of that corner of the bedroom. It can wait till my next Lowe's trip though; the circuit is presently idle. It ain't gonna overheat with 0.00A flowing through it.

    As for "proper supports"... that's where I wish I had a better definition. I don't have any background that would help me calculate the support requirements. For that matter, I can't prove that what's there is inadequate, only that when I look at it and contemplate the weight, I get a supercharged case of the screaming heebie jeebies.

  15. #30
    Retired Defense Industry Engineer jadnashua's Avatar
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    You talked about cantelevers. You don't want a diving board. You need to find some way to support the subfloor, whether you add some stuff to the existing framing, or other existing structure, then build something up from below on that spot.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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