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I have read another thread concerning the elevation of electric water heaters but nothing seemed to address my particular situation: I live on a barrier island and it floods here every couple of years during hurricane season. Water has been in my garage as high as chest deep, though the usual flood is no more than a foot deep. The house is built on pilings. I have a 12 foot ceiling in the garage downstairs.

My water heater is currently located in a walk-in attic upstairs but the thought of having water above my living spaces makes me very uneasy. I want to move the heater downstairs into the garage and build a 5 feet tall platform for it out of pressure treated lumber: 4 X 4s for the legs; 2 X 4s for the platform deck. I would secure the legs of the platform to the concrete floor with 90° braces so it doesn't float off. While the garage is not heated, I've never seen it get below 50°F inside in the winter; nor above 80°F in the summer. Outside temps vary from about 12° to as much as 100°, though either extreme is very rare.

Does anybody have any thoughts about this? Something I haven't thought about? My plumber estimates moving the current heater will run about $275-300, assuming I build the platform.

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    Consider going tankless – agentp Jan 24 '18 at 13:06
  • Do you mean for the house to be occupyable during storms? Or do you evacuate? – Harper Jan 24 '18 at 21:23
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    Moving the water heater from the attic to the basement is only $300?! That is either incredibly good luck, a bad estimate, or overlooking many aspects of the plumbing. – wallyk Jan 24 '18 at 23:20
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    Wouldn't it be easier, cheaper, and acceptable to add a deep overflow pan under the attic water heater to address your concerns? – wallyk Jan 24 '18 at 23:22
  • i would have thought there would be a overflow pan in the first place. One other thought here, since you are obviously in a flood zone there likely are legal, zoning, and insurance issues to consider before putting it in your garage (that's why its in the attic to begin with) – agentp Jan 25 '18 at 15:53
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In Dallas many houses have water heaters in the attic. This frees up usable space in the living areas, but I have heard from someone in water damage remediation of virtually total loss of a demi-mansion due to the simultaneous failure of multiple electric water heaters while the family was on vacation.

We have lived in our single story tract house for 40 years and had two different gas fired tank water heaters fail. This caused significant damage even though we were home both times. Our heater is not in the attic but in a service closet on the living floor in the middle of the house.

Thirteen years ago I changed to a tankless heater and feel much more comfortable. I put the tankless heater in the same location as the old tank and if it would leak catastrophically it would cause some damage, but the service life of these tankless heaters is much longer than a tank, and I think the tankless give more warning of impending failure.

In your situation you could consider putting a tankless heater on an outside wall of the outside of the house near where the current tank is. These outside tankless heaters do not need a flue through the attic and roof and if they leak the water runs down the outside wall.

One limitation of modern tankless gas fired heaters is that they require 120 V AC power to operate the controls (and a small heater on the outside models) so if the line power is out, you have no hot water (unless you have a backup generator). We have a first generation Bosch tankless (which has a standing pilot light--yikes!), but it does not require line power so we would have hot water even if the power is out. We have had winter outages of some extent in Dallas--ice storms bring down power lines, but when we replace our existing heater it will be with a modern tankless requiring line power.

EDIT

The major drawbacks of a tankless water heater (besides cost, they cost significantly more than a tank) are:

  1. The tankless have a much larger burner (200 kBTU/h or more vs ~ 40 kBTU/h for a 40 gal tank) and this may require a larger gas pipe, although this may be only from a place already in the house, i.e., the existing buried gas line from the meter to the house is probably sufficient.

  2. The tankless will not supply the volume of hot water that a tank will--until the tank is depleted.

  3. The tankless has more complicated controls which cannot be expected to be as robust as the simpler controls for a tank and will cost more to repair.

I recently talked to a builder who built a small subdivision of 40 or so houses. He offered a tankless water heater hung on an outside wall as an option and few if any purchasers took it. He selected it for his own house and he loves it. Unlimited hot water no matter how many house guests.

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    If frequent power outages are a concern, you can use a battery backup (like you'd use with a computer) on your tankless. Also, for extra leak protection you can install an electronic safety valve on your house main and locate a leak sensor near your water heater. – Shimon Rura Jan 24 '18 at 15:45
  • Yes, a battery backup would work very well on a gas tankless. I would consult manufacturers and see if they have any 12V or 24V solutions, as it's far more sensible to run the tankless direct off battery than run an AC inberter for what are in fact LVDC controls. See also use of gas tankless on RVs, boats, etc. – Harper Jan 24 '18 at 21:21
  • I probably had the same pilot based bosch aquastar that jim has good unit it has been in since 2000 , they did have a battery backed unit I think 12v ignitor and I thought one more thing to go wrong and went with pilot version. – Ed Beal Jan 24 '18 at 22:49
  • Tankless water heaters are also more susceptible to scale buildup in hard water areas. Unlike tank heaters where you flush the tank by opening a valve, you need a special pump and chemicals to flush the tankless heater annually. If they did not install a valve to do this, you have to disconnect the whole thing from your plumbing. – user71659 Jan 25 '18 at 1:16
  • I have had my tankless water heater "professionally" descaled once. Yikes! The supposed expert couldn't figure out how my special isolation valves worked in the millisecond he allotted to that analysis and before I could move or even speak he magically pulled a large wrench seemingly from nowhere and twisted the valve the wrong way over the stop! The valve is fairly robust so after he left I was able to remove the handle and get the valve into the correct state again. The only chemical he used was ordinary white vinegar (5%) and a submersible pump. – Jim Stewart Jan 25 '18 at 13:35
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Putting a water heater on a platform in the garage is not only common in the US, it's code in a lot of places. Code requires the heater to be elevated at least 18" IIRC, to help keep it above any flammable vapors that might be present in the garage (e.g., gasoline).

My concern with your plan is that you want to elevate the heater 5', not 18". You'll have a bear of a time wrestling the water heater up that high (though, maybe not any more than you would getting it into the attic), but I'd be worried about it falling. As far as I know, code doesn't require the heater to be secured to the wall when elevated 18", so an additional 3.5' shouldn't change much in that regard, but you may want to build in something to your platform as an anti-tip mechanism. It may be as simple as a board placed across the front near the top of the heater, which can be easily removed if needed. You'll also want to make sure your (very top heavy) platform is extremely stable - several hundred pounds of tank and water 5 feet in the air on a wobbly platform is a recipe for disaster.

  • We have a code requirement for a strap on water heaters I believe California also has this requirement because of earth quakes. – Ed Beal Jan 24 '18 at 22:44
  • Two straps are required with natural gas and propane water heaters in Oregon and Washington too. – wallyk Jan 24 '18 at 23:17
  • The requirement for elevating the water heater has been largely dropped since FVIR water heaters became fully mandated in mid-2005. – user71659 Jan 25 '18 at 1:07
  • You should see the platform I built for the whole house generator. You could park a truck on it if it would fit. Very stout and on pilings held in place with poured concrete. It's neck high and you would have enjoyed watching myself and one other retired guy like me get that 450lb generator five feet in the air. But where there's a will, there's a way. – Jay Hanig Jan 28 '18 at 9:40
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I suggest you to go from tanked to tankless heater and to keep it in attic, so if it fails you'll not get a plenty half cubic metre of hot water rinning in your house but only what pipes can carry (and also cold water).

Or just put a tankless inside and a tanked solar-powered on the roof, so if it fails, it' wouldn't be worst that a heavy rain and you'll also save a lot on heating DHW, using tankless only when sun isn't enough.

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