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Tankless Water Heater Installation

I'm installing a tankless water heater soon and have some questions about the best way to install it. It is replacing a tank unit that was installed before in-home installations were made illegal. The tankless unit will be either put in place of the original water heater which is located in a closet behind a dry bar and near the laundry area; or possibly in the attic above the laundry area. Is there any reason not to install the unit in the attic if it is given the proper clearance (12") to the top, bottom and front? The only thing I can think of is the summer heat; our area can reach 105 in the summer and the attic might get as hot as 140 on a warm day. Will warm temperatures cause electronics problems? The unit (a Rheem Eco200-DVN3) does have a remote thermostat circuit board, so is it possible that any heat sensitive electronics would not be located in the attic?
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Posted 2011-03-12T05:48:53+0000  by RustyNail RustyNail

Hey RustyNail,


Thanks for your question and welcome to the community!


You have made a great choice in getting a tankless water heater and replacing your old tank. 


The best and easiest option for your new water heater is to install it where the old water heater was placed, in the closet behind the wet bar. Installing it in the attic is an uncommon practice that would require not only running more pipe and power supplies, but it runs into needing to follow any local codes so you don't run into any issues after installation. Always consult a licensed plumber/installer if you have any specific questions that deal with codes or regulations, as they can vary from state to state, even city to city.


Our water heater expert on the community, ChrisFixit, and I agreed that putting your new tankless unit where the old one has more advantages than attic installation:



  • You won't have to re-run any existing supply pipes or power up into your attic, installing it in the closet behind the dry bar will mean you will have to make only minor adjustments to the pipe and electrical connections.
  • Having your new tankless heater unit closer to your water supply source (ie. in the closet vs.. higher in the attic) will create less issues for you further down the road
  •  The only real remaining installation to worry about it replacing the vent pipe to stainless steel, as tankless units create more condensation than regular tank models, but that is a simple replacement since the pipe is already there from the old unit
  • The only time that attic tankless water heaters are installed are typically in warmer climates like the Caribbean and they are solar-powered, hence the need for them to be placed higher in the household
Basically, installing the unit inside the attic can be done, but it would require extra work, and knowledge with your local codes, etc.
Finally, I'm going to give you a link for Rheem's tankless water heater page, they have great installation tips and troubleshooting know-how, the page can be found here
We hope this answers any questions you had, and please let us know if we can further assist you.


Posted 2011-03-12T16:13:31+0000  by Joseph_HD_ATL
Thanks, I have already given these issues some consideration. The closet location would require re-locating the water and gas supply lines (opening the wall), re plumbing the over pressure safety drain and condensate drain over to the washing machine, about 3x the amount of the expensive ducting to reach the roof fitting, and another gas line run horizontally to supply a new gas clothes dryer and a future gas range installation.

If I install the unit in the attic, the gas line and the drain lines would drop straight down to the laundry room. All of the plumbing for the hot and cold water is in close proximity to the tankless heater location, and the hot water runs to the bathrooms, laundry and kitchen become shorter. I would only need a single 3' long duct to exit the roof instead of 2 3' ducts 2 45's, an adjustable length section, and a fire stop plate (about $250 in ducting).

So my biggest concern is about the internal electronics on the water heater being exposed to 140deg or possibly more temps in the summer. I called Rheem yesterday and the response was 'Yes you absolutely can install it in the attic'. But the same person also said that it must be attached to an exterior wall, which makes no sense, so I don't have much faith in their customer support. If every installation required an exterior wall then there would be no need for roof-top ducting!!
Posted 2011-03-12T20:53:45+0000  by RustyNail

It sounds like you have done your homework! :smileyhappy:


Since you have all of your workings done, I would still say to check with either a licensed installer of Rheem, or if you can get a localized dealer that has had this before concerning the internal system for the unit.  Again, just make sure when you are arranging your pipes make it accessible in case of any further maintenance down the road. 


As for checking your internal electronics not failing at 140 degrees, you should be able to contact Rheem again, and this time speak to their tech department regarding exact specs. Most of the tech guys are always a separate dept from the troubleshooting department and can give you a more definite answer. Since its not an item that we don't sell (at least in my area) in the store, I unfortunately can't check to see if there are any additional information on it. 


You know what you are up against and what is next in the install process, my hats off to you on making this work!



Posted 2011-03-12T21:38:43+0000  by Joseph_HD_ATL

Hello RustyNail and welcome to The Community!  I have been a part of several tankless water heater installations and they are definitely one of my favorite products in the store.  You have definitely done your homework for this project.


I have several areas of concern to add to the excellent comments made by aboveaveragejoe and ChrisFixIt.  First, I am concerned about the attic temperature reaching up to 140 on a warm summer day.  Do you have an attic fan installed to reduce the temperature in case you need to go up there in the summertime?  This temperature may also create problems with your roofing system.


Second, will your water pipes require insulation against freezing in the winter?  Since the operation and efficiency of tankless water heaters depends upon the temperature rise, pipes cannot freeze. 


Third, the vertical vent kit up through the roof will give you the most cost-effective solution.  Be sure that making a hole in the roof does not affect any roofing warranties.


Last, you may have been told that the unit should be installed on an exterior wall since most attics do not have “interior” walls or room dividers.  You may want to contact Rheem  (1-800-720-2076 with your model and serial numbers) to see if you could create a sturdy “false wall” to obtain the best placement of the tankless unit in the attic.


Please keep us posted on your progress and best wishes on this project!

Posted 2011-03-15T15:01:13+0000  by Eileen_HD_ATL
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