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Glenn, Electrician
Category: Home Improvement
Satisfied Customers: 2311
Experience:  former journeyman electrician /maintenance mechanic for 30 years
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How to add a second hot water heater to home?

Customer Question

Here is my question.
1. I have a new 80 gallon electric hot water heater fully installed and working in my 3 full bath home with 5 family members that includes teenagers and thus every morning when everyone showers in a row we always run out of hot water.
2. I want to install a second 50 gallon hot water heater next to the 80 gallon heater and hook this up in a safe way.
3. I think the correct way to do this (I will not do it myself, but hire a plumber), but most plumbers have not done this and I want it done right.
4. I think the correct way is to have cold water input into each of the two hot water heaters. Then, have each of the hot water outlets hooked into the hot water line of the house. Then, install an expansion tank on I think each of the two hot water heaters so that the combined expansion of each tank does not over pressure the house system?
5. Have I missed anything?
6. The reason I want the second tank to be 50 gallons, vs the original new tank of 80 gallons is that the second tank will then fit nicely next to the 80 gallon.
Thank you

Submitted: 11 years ago.
Category: Home Improvement
Expert:  Glenn replied 11 years ago.


I think you are on the right track, but I don't see the need of an expansion tank. I would hook both heaters up like you said. Another possibility is to hook the 80 gallon tank up to the cold water as a "pre-heater". The hot water from this tank will then go into the 50 gallon "inlet" from there, the 50 gallon tank "outlet" (hot) will connect to the house hot water supply. This will allow you to pre-heat 80 gallons of water to, say, 110-120 degrees. Set the 50 gallon tank at 130 - 140 degrees (less on both tanks if you have kids!!). Now the 50 gallon tank will supply the hot water for the house and if you run low, the water has already been pre-heated to 120 (or

so). This way, you will realize an energy saving...heating both tanks to the same temperature, you will not!!!...Makes sense????

Customer: replied 11 years ago.

Here is my problem. I have had Lowes reject the solution of a second hot water heater saying it is not safe as it creates too much pressure. I need advice from an expert who flat out knows 100% for certain, not 99%, how to make the solution safe and work. I know it can be done because I was once involved with a hotel that had a hot water problem in some condos not attached to the hotel and they did a multiple household hook up of hot water tanks but the plumbing was done in such a way that was safe and I no longer have contact with the hotel and thus do not know the details. I want someone who either has done this or is 100 %, not 99% sure of the solution.

Expert:  Glenn replied 11 years ago.

I agree with the idea that it will save you money. As far as 100%, I am 100% sure you will not have a water pressure problem as long as you keep the thermostat settings below the stam mark which would be atleast 212 degrees and a water heater will not go up that high. I have installed many the way I told you and NEVER had a problem