Dual water heaters - can I disable one?

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We recently bought a new house that has dual 50-gallon electric water heaters. Each heater has a single 5500 Watt heating element.
The 'problem' is that there are only two of us living in the house, and we very likely don't need 100 gallons of hot water standing by. The electric bill is out of control, and we're thinking the dual water heaters are a chunk of that.
The two heaters appear to be plumbed in parallel rather than series. Can I turn off the cold water inlet valve on one heater and unplug it to save some electric power? Do I need to drain the heater that I won't be using? Should I take the extra step of connecting the inlet pipe to the outlet pipe, (on the plumbing side, not the heater side), in order to completely bypass that heater? What else might I be missing?
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On 06/03/2014 12:15 AM, Jim Joyce wrote:

Then I'd drain and remove the unused one.
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I've flush it, drain it, and shut the valves off. Kill the power, of course. If the space is not a problem, you'd have a spare ready to go when the other one fails.
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On 06/03/2014 04:56 AM, Ed Pawlowski wrote:

I agree that it would be a good idea to take one out of service but I wonder if it would be better not to drain it. The minerals in the water could solidify and clog the heater.
I'd probably rotate their use every six months or so.
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On Tuesday, June 3, 2014 12:15:57 AM UTC-4, Jim Joyce wrote:

Unplug it? Maybe it's on a plug, but all the electric WH's I've seen were wired in. Nat gas ones that have a blower, those are on cords. If there is no plug, maybe you can open the breaker, but not sure if they would have separate breakers or be on one larger breaker
But if you want to disable one, I would just do what you suggested, turn off the water supply and electric. I've done that with nat gas ones that were in parallel where the house didn't really need two. One problem though is that you only have 5500W? That's small for a 50 gallon, the recovery time is going to be slow, and with only one, you might run out at times, but you can try it and see.
From a longevity standpoint, you might be better off fully draining it, leaving connections open so it could dry out. Not sure what effect that would have in terms of keeping it good for future use versus leaving it full of water.
It will save some money, but I doubt it's the source of much of your bill. Whether you have one or two, it's going to take the same amount of electricity to heat the water you use. The only thing you'll save is the standby losses on the second tank. Electric ones are fully insulated, have no flue up the middle, so I doubt it's going to make much difference, but it will help.
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On Tuesday, June 3, 2014 9:03:08 AM UTC-4, trader_4 wrote:

You'd be surprised. We had a vacation house and I put a 30amp double pole switch in the hall to turn off the water heater when we were not there. Knocked 30-40 bucks off the bill.
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On Tuesday, June 3, 2014 4:47:13 PM UTC-4, jamesgang wrote:

I guess it's possible it could be in that range. I was winging it off the fact that the standby from my nat gas WH can't amount to much because in the summer, my whole nat gas bill is $17 a month. I was figuring most of that was for actual water heating that was used. But maybe most of it is from standy, I really have no way of knowing If say $10 was from standby and then you factor in that electric costs about 2.7 times as much, that would give you $27 for an electric one, which is near your numbers. Whatever it is, if the OP doesn't need that extra tank, turning it off will make a worthwhile difference.
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Thanks, Jimbo. The two heaters are in a closet in a corner of the garage, so I like the idea of leaving the second one there for future use, or rotating their use, etc.
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Right, space is not a problem. I like your approach. Thanks.
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Just a few weeks ago we flushed both heaters, which probably hadn't been done since the house was built in 2006. (We just bought the house in August of last year.) Wow, what a load of mineral deposits! Milky white water and an endless supply of 'chunks'.

That would be easy since both are in a cabinet in a corner of the garage. Thanks.
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On 06/03/2014 05:42 PM, Jim Joyce wrote:

The reason I suggested rotation :
I rarely use the hot water on my washer but needed to do a load the other day using hot.
The pipe was clogged.
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wrote:

Each of these have a standard 240V plug, the same type as my clothes dryer, and they share a breaker in the electrical panel. I flipped the breaker off and unplugged them when I was flushing out the mineral build-up.

Our last house was nearly the same size and had a single 50-gal heater, but that heater had both a lower element and an upper element. I'm not sure of their respective wattages.

When we moved in, we didn't have *hot* water, which eventually prompted me to check the heaters. One's overtemp limit switch was tripped, so we had been running on one heater with the second one providing unheated water. When I reset the overtemp limit switch, the following month the electric bill went from $78 to $142. I'm sure there were other things involved, but I'm hoping the biggest chunk of that jump was the second heater.
Anyway, thanks everyone. For now, I'll flip the cold water inlet valve off and unplug one of the heaters. We'll see how things go, as far as temperature and supply. I don't think I'll drain it for now, in case I decide to rotate the heaters every X months.
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Absoluely don't remove a good WH. Besides the one in use failing, what if four people drop in to visit you, your family or refugees from a fire or flood? Even if they live in a camper outside, you might want them to take hot showers inside.
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Plainly, the installer envisioned running only one of them some times.

Wow!!!!! I would have thought the difference would be very little. Please post back with next month's bill, and how many days in each billing month.
Maybe you have a dripping hot water faucet.

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Jim: It's actually a good idea to have two water heaters plumbed in series. That way, if and when one water heater kicks the bucket, you can simply switch over to the other water heater while the first one is being replaced.
Also, you can use that second water heater while doing maintenance on the first heater, like replacing the anode in it. That way you're not in a situation where you go without hot water unless and until you can replace the anode.
--
nestork

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On Monday, June 2, 2014 9:15:57 PM UTC-7, Jim Joyce wrote:

<snip> Just curious here. I have never heard of a WH with only one element and later you mention them being on 240 plugs.
Could you post the make and model, I'd like to look them up as one might work in my house.
Harry K
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it might be more cost efficent to heavily insulate both water heaters. with electric water heaters it easy to add a water heater blanket
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On Wed, 4 Jun 2014 16:42:16 +0200, nestork

All that follows is true about in parallel too, right?

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The outer surfaces of the water heaters aren't noticeably warm, so I think (lack of) insulation isn't an issue in this case. Thanks for the suggestion though.
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On Monday, June 9, 2014 1:57:58 AM UTC-4, Jim Joyce wrote:

The outside of a house isn't warm to the touch either, but insulation is still important. How much difference adding insulation might make, IDK, but I don't necessarily think the warm to the touch test means that more insulation won't make a difference. And insulation for an electric will be more effective because there is no flue up the middle and you can put insulation on top too.
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