Two hot water heaters


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Old 01-21-14, 10:34 AM
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Two hot water heaters

I've been trying to read up on this, but really can't find anything to fit the situation that I have. I have a ranch house with a gas hot water heater. After I bought the house, I built an 800 sf addition with a new master bedroom and bathroom and decided it would be a good idea to run a separate hot water heater for the addition (helped with ease of installation also). In the new master bathroom, we have a shower that has the overhead rain head, 4 wall jets, and a handheld shower head. I figured that since the addition was only serving one bathroom, a 40 gallon hot water heater would be fine. Unfortunately, at the rate the shower goes through water and the fact that my wife likes the water scalding hot, she can go through nearly an entire tank in one shower. To remedy this, I'm wondering if I can tie the hot water outlet pipes from both hot water heaters together. One is gas, one is electric, and they're about 60' apart. I am not a plumber and really have no idea if this is acceptable....but it seems that it would work in my engineering based mind.

Additionally, we have a big jacuzzi tub that has been used only 2 or 3 times in a year and a half because there isn't enough water that is hot enough to make it enjoyable to my wife. If we could tap into the water in the other hot water heater, then I'm sure this would finally get some use!

Any help would be greatly appreciated!
 
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Old 01-21-14, 11:27 AM
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Yea, it can be tied together and that's how my house is plumbed. I also the ability to shut off one heater and run the whole house off the other. Great during prolonged power outages to run off the propane heater. Also when we have large parties I close the cross feed valve so guests can't deplete the master's hot water. The key though is that we do not use so much hot water at one time that it would use all the hot water from one tank.

There are limitations to running two heaters in parallel especially when they are in different locations. Water will take the path of least resistance. So if one heater is closer to the master shower and can flow water more freely than the one further away it will do most of the work. I don't think it's all or nothing but I'm certain the flow will not be perfectly balanced. Suppose your master shower pulls 60% from the close heater and that heater runs out of hot water. Your hot water is then only 40% hot water from the other heater. Not ice cold but enough to curtail your shower. It's not the end of the world however. If that 40% is enough extra capacity to get you through a long shower or fill that big tub then it's enough.
 
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Old 01-21-14, 11:36 AM
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Hmmm... Not that it matters now but I assume you did not take permits out?

Typically you would not pass inspection if the heater cannot fill the large tub/jacuzi..

Anyway why is the one heater still electric?

Which heater feeds the master? Gas or electric?

Ideally you want the gas to feed the electric... Hook them up in series.....I say this becuase of the two different types of heaters and space between them...

 
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Old 01-21-14, 01:42 PM
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Yes, we did have a permit when we built the addition. I know the heater can fill the tub, just not to the temperature liking of my wife If I were to take a bath, I'm guessing there would be plenty of hot water to get to the temp I like.

The original in the house is a gas heater. I planned on installing a gas hot water heater in the addition (I actually had it purchased and installed), but realized after it was too late that a standard gas hot water heater has to be vented above the gutter line to pass code. I didn't know that when I was building the addition and didn't realize it until it was too late (everything was done and closed in), so I had to resort to an electric one in the addition. I know there are some gas ones that have powered ventilation systems that can be vented below the gutter line, but I was at the end of my budget and went with the cheapest method at the time.

So the electric feeds only the master and an outside hose bib and the gas feeds the rest of the house (other bathrooms, washing machine, dishwasher, sink, etc.). I thought about hooking them up in series, but that would mean running two lines instead of one. If I run the gas to the electric, then I would also have to run a line from the electric back to the original outlet for the gas, correct? I was trying to make it as easy as possible and hoped that adding a T in each outlet and running them together might be a relatively quick and cheap "solution" to my problem.
 
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Old 01-21-14, 01:46 PM
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Thinking about this a little more, maybe series does make more sense. The electric is considerably more expensive to run than the gas, so maybe running the gas to the electric would cut down a little on my electric bill. Maybe the extra $100-$150 worth of copper is worth it in the long run.
 
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Old 01-21-14, 03:09 PM
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Also, are you absolutely sure that you don't have one dead element out of the two, in the electric water heater.

I just can't imagine a person using 40 gallons of hot water in one shower.

Anyway, I haven't met your wife so I am probably wrong. I just thought I would throw that out there for consideration.
 
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Old 01-21-14, 03:17 PM
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then I would also have to run a line from the electric back to the original outlet for the gas, correct?
No... Disconnect the cold from the electric... Then add a tee to the hot line from the gas water heater to the electric... When you run this line add a check valve on that line...

This way the master will draw from both and the other bath will draw from the gas only....

Do you need the check valve??? Probably not but I would add one anyway...
 
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Old 01-21-14, 07:11 PM
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I just can't imagine a person using 40 gallons of hot water in one shower.
I can.

smkilian
Thinking about this a little more, maybe series does make more sense. The electric is considerably more expensive to run than the gas, so maybe running the gas to the electric would cut down a little on my electric bill. Maybe the extra $100-$150 worth of copper is worth it in the long run.
I agree with Mike and I also agree that this should cut your electric bill a bit. It would have to be cheaper to maintain hot water temperature with electric than to actually heat and maintain it with electric.
 
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Old 01-22-14, 10:34 AM
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I think I'm going to go ahead and put a T in the hot water outlet for the gas one, then run that with a check valve inline over to the input on the electric one. I really think that sounds like it would best help my situation.

As far as the 40 gallons in one shower goes, my wife turns the water on to as hot as it can get (I have no idea how she can do that) and can be in there for 10-15 minutes. At 2.5 gal/min on the showerhead and 1.75 gal/min each on 4 wall jets when she uses them, 40 gallons of hot water really isn't that much.

Thanks to everybody for the help! I greatly appreciate it!
 
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Old 01-22-14, 11:26 AM
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Let us know how it works out... You should save on your electric bill IMO...
 
 

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