Water Heater duplex puzzle - Tankless or Attic Gas?

Question

I own a split duplex in Nashville TN that has two gas water heaters in the attic above each apartment bathroom.

It was fine for 7 years, but one day the temperature dipped down so low, a burst pipe destroyed the unit. Thankfully we were insured and it was covered and restored to good as new, and the original water heater wasn't damaged, just the pipe.

Now years later, this water heater is ready to die. It's been a long time question for me whether or not I should continue replacing the water heaters and ensuring proper insulation in the attic, or if I should relocate with a tankless water heater downstairs.

I had a few plumbers come out, in addition to the folks who restored after the flooding, and all of them agreed that there is not enough square footage in either apartment to relocate the gas heaters unless I convert to a SFH and remodel, and no room in the crawlspace under the house (about 2 ft tall) to install a low boy UNDER the bathrooms.

I believe if i want to relocate from the attic, I have to do tankless in each unit, but I'm wondering if it's worth the cost.. or if I should just stay the route in the attic. This is a buy and hold.

If anyone has any advice, or went through this themselves, please let me know!

I also can't seem to find any plumbers who are familiar with tankless, which is concerning.

John Warren · Answer

@Robin W. I would stick with the current set up. If you are worried about freezing during the winter you can always add a small electric heater. I did this in a basement at a building I own in Berwyn where the pipes froze during the "polar vortex" in 2018. I used an electric baseboard heater on a thermostat so that it would turn off automatically when it got warm outside.

JD Martin · Answer

Thoughts:

1. WHs in attics are water time bombs. Eventually all water heaters leak. They may also blow off the temperature relief valve due to internal faults or excess system pressure, from a closed loop, failed prv, etc.

2. Consider switching to electric. I prefer gas but electric gives you more installation options (no venting). If the crawl doesn't flood you can dig down to install a shorty. You need to have 30 amps free in your breaker box. The monthly cost for electric vs. gas isn't much here in TN. I was a plumber in a former life and we installed shortys in crawlspaces lots of times, and yes sometimes it required a half shovel. As long as you can keep the base dry and you can put a disconnect panel in they can go almost anywhere.

Marc Winter · Answer

If you can't get it out of the attic, make sure to put a deep plastic container under it.  They come with a hose type bib opening on them and you can plumb that to wherever is most convenient.  That way if the heater rusts out or the pressure relief valve blows, it won't (hopefully) flood the apartment under it.

Lastly, install a moisture sensor in that pan that will sound an alarm so everyone knows something is up.

JD Martin · Answer

Ha! That's because most plumbers (myself included) hate digging in crawlspaces. You have to use a half shovel and you're usually hunched over.

If you have an area that can be insulated and enclosing outside you can do that as well (suggested above). I have one house like that with no problems whatsoever, and the heater has been out there for 30+ years (I just replaced it because the elements burned out and it's 30 years old).

If you put it in the crawlspace just be sure that it isn't sitting in dirt. You can use a plastic heater pan or even the bottom of a plastic 55 gallon barrel. Also be sure the pop off valve is piped to daylight or at least to downhill from the heater. And remember you don't want to go this route if the crawlspace floods, if you can't get it off the ground.

PS: I forgot to mention that if you have to dig it in you have to use mechanical pumping to drain the tank if it becomes necessary. You can still flush it under pressure - you just have to make sure to dig out enough access to open & close the drain valve. The valve can be rotated so it faces sideways to allow a hose to be hooked to it.

Devan Mcclish · Answer

@Robin W. relocate them to the exterior and put heat boxes around them. Did this on a STR we owned, never had an issue. Even when we sold it, the home inspector had no problems with it.

Robin W. · Answer

Account Closed There is no gas line right now, as all the units have electric wall heaters, and window AC units. Tenants pay utilities.I AM considering for the future a HVAC conversion,  but I wasn't thinking about doing it all at once. Quotes were pretty high last I checked for HVAC conversion of each unit, plus getting city to hookup gas.

But if there's merit to having gas water heaters outside in a custom-built insulated enclosure then maybe there is a case to biting the bullet.

Account Closed · Answer

@Robin W.

Oooooooh kayyyyy. If there’s no gas line service it’s highly unlikely I’d go to a gas one exterior mounted. Last quote I had which was a month ago my provider wanted $14k to run a new line. I pointed out the old one was run incorrectly and thankfully they saw the light and covered the cost entirely. Take about a million years to recoup $14k.

Account Closed · Answer

I’m in a entirely different environment but I would relocate outside and go gas. Here, electric is ~3x the monthly cost (but 2/3 purchase price). Coat closets sound good until you said 1 bedroom units.

Justin Tahilramani · Answer

If it has two water taps, which I assume it does, you will need two tankless units. That said, they *COULD* both be connected to the same propane tank. I don't think it would be any more expensive than your current quotes and you wont have ugly protrusions built onto your house to hide water heaters. You would also solve the issue of venting and potential leaks in the unit. While they may be more expensive to maintain, it sure beats units in an attic or destroying the look of your property with an ugly add on. Just my two cents.

Or, as others have suggested, dig out the crawl and install shorty units.

Water Heater duplex puzzle - Tankless or Attic Gas?

Most Popular Reply