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Thread: Tankless + Tank Code Legal?

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  1. #1
    DIY Junior Member mikeinkirkland's Avatar
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    Default Tankless + Tank Code Legal?

    I'm not sure where I should have posted it, but I have a question if it's code legal to put a small tankless electric hot water heater in series after a tank heater to supply the entire house. It's a vacation home and the idea is to not keep the tank hot all the time but still have at least some hot water available when you first arrive at the house. See:

    http://www.terrylove.com/forums/show...ries-with-tank

  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    You can install any combination of heaters in a home.

    My question is if the above scenario is code legal? Can you put a small tankless unit designed for point of use with 1/2" fittings in series with the main hot water line for the entire house?
    If your water heating need requires pipe sizing to 3/4", then you will need to find a heater that passes through with 3/4"
    Last edited by Terry; 02-11-2012 at 07:07 PM.

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    Plumber Winslow's Avatar
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    If you have a tankless water heater then the only reason to have a tank is if you have a recirculating line. The tankless will provide hot water as quickly as a tank. Having a tank sitting there heating water while noone is there will defeat the purpose of not buying a properly sized propane tank. Why not just put your tank on a timer and set it up to turn on the heater when you will be there?
    Last edited by Winslow; 02-12-2012 at 08:54 AM.

  4. #4
    DIY Junior Member mikeinkirkland's Avatar
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    Quote Originally Posted by Winslow View Post
    If you have a tankless water heater then the only reason to have a tank is if you have a recirculating line. The tankless will provide hot water as quickly as a tank. Having a tank sitting there heating water while noone is there will defeat the purpose of not buying a properly sized propane tank. Why not just put your tank on a timer and set it up to turn on the heater when you will be there?
    Thanks for the answers. The problem is it's a vacation home and the usage won't follow any consistent schedule. It's a big waste to heat 40 or 50 gallons of water routinely on some schedule when nobody will be there to use it. If there was enough electrical service to run a big enough tankless I would go that route, but there isn't. 7.5KW is about the most I can get away with (the house also has electric heat and is on a 25 KVA shared transformer).

    I may have to get more creative like having the small tankless service just one bathroom.

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    Do you have landline telephone service at your vacation house?

  6. #6
    DIY Junior Member mikeinkirkland's Avatar
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    No. If it had a full time internet connection, or even phone line, I know I could do a remote system to heat up the tank prior to visiting. But these days everyone in the area just uses their cell phones for voice and data. But that won't work for remote access.

    But thanks for the answers. It's good to know a tank + tankless can be code legal. The only issue in this case is the line size. I'll probably just have the plumber add two ball valves and a temporary "loop" where a tankless could be added in the future. That will hopefully pass inspection and make it easy to add a tankless in the future.

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