Water heater in unheated attic

[Ashful]

One of the peculiarities of this old house is that we have a water heater located in an unheated attic space, feeding just the sink and shower in one bathroom on our fourth floor. This has been used solely for guests and emergencies the last dozen years, although with kids now into their teen years, it's probably not long before one of them chooses to move up there to the little suite for a little more privacy and autonomy.

The water heater is about 15 years old, and being above several floors of original old plaster we don't want damaged, I'm thinking it'd make more sense to replace it now, before it leaks. It was also (stupidly) installed in a shallow pan, which makes it impossible to connect any hose to the drain cock. Careless prior owners / plumbers.

Fuel available is electric or propane, although venting requirements may favor electric. I'm sort of interested in options for on-demand, given it's low-usage and dedicated to only one bathroom immediately on the adjacent wall, but I have concerns about it freezing. We get sub-zero here, not frequently, but maybe 1 - 3 evenings per year. We can have long stretches of single digits, and I suspect that attic is well below freezing at these times. The water heater keeps the insulating piping warm enough that this is no concern, but do on-demand systems have freeze protection? Do they have to cycle all night to keep from freezing on cold nights? If so, that might also favor electric.

 

[stoveliker]

You'd also likely have to run a larger power line to the attic if you go with on-demand? If so, that would add cost.

 

[EbS-P]

Is the layout of the bathroom conducive to pitting an on demand electric unit in like under the sink. Takes 40-60 amp.
Your friend has shared a link to a Home Depot product they think you would be interested in seeing.

Rheem Performance 13 kW Self-Modulating 2.54 GPM Tankless Electric Water Heater RETEX-13 - The Home Depot

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Water heaters up there are a big storm away from a big mess under. Just as Texas.

 

[Ashful]

I have 100 amps up to that attic, and I have to verify, but I think there may be enough capacity on it to handle an on-demand electric.

Sink is pedestal, and anything is possible, but I'd really hate to muck up a very nice bathroom with a water heater under the sink. Better yet might be to just bolt it to partition wall separating heated bathroom from attic, put an insulated chase around it, and then remove insulation from wall between bathroom and the chase.

Most of my day got eaten by a workstation taking a nosedive, but while waiting for hardware scans and backups, I was able to do a few quick minutes of reading. It seems some systems do have freeze protection for the unit itself. Specifically the gas-powered units from Rinnai and Rheem have ceramic resistive heaters that cycle on when the unit itself gets into the low-30F's. I'm not sure this would generate enough latent heat out thru the piping to keep the pipes from freezing, though.

Here's a photo of the setup I happened to have handy. Chimney is to the left (with signatures of the builders and the 1770's inhabitants of this house scratched into the wet stucco), and the bathroom wall is behind the water heater, in this view. Lots of exposed plumbing, which could be all cut out and re-done either inside the wall, or within a secondary chase.

 

[Ashful]

One thing that's been amusing me is the constant claims that, because a tankless water heater doesn't store 60 gallons of water, they can't leak. As if a heat exchanger exposed to water on one side and flame on the other could never develop a leak! This thing is going to be connected to my 10 GPM well pump, such that if there is a leak in either type of water heater, the stored water in a tank is the least of my concerns.

But it does raise a question about probability of a leak. My last traditional electric tank water heater went from 1996 until 2020.... 24 years. That seems to be longer than the claimed 20 year service life on most tankless water heaters.

Maybe only the insurance companies know the truth.

 

[stoveliker]

I agree re:leaking.
I'd still add a big enough tray (with water sensor alarm) below anything tankless that might end up in the attic.
Water in the attic just sucks - because it tends to go down and the whole home is beneath the attic.

 

[Ashful]

I agree re:leaking.
I'd still add a big enough tray (with water sensor alarm) below anything tankless that might end up in the attic.
Water in the attic just sucks - because it tends to go down and the whole home is beneath the attic.

Thinking thru this more, I have a water leak sensor in the tray under my water heater. My theory is that when the tank begins to weep, my water sensor will catch it, trigger my alarm system, which will then turn off water to the whole house and trigger an alarm.

If the owner hadn't buried the drain cock in the pan, and also failed to install a boiler drain on that line in the basement, that would be my time to go shut off that feed and drain it down. But since they did omit both, it'll be my time to start cussing and scrambling. Whatever goes up there next, there WILL be access to the drain port, and there WILL be a boiler drain installed downstream of the shutoff valve to this attic.

If I put a drain pan under the tankless, I could set the same water alarm sensor in that, and just pray for a miracle in which the leak actually lands in the pan, versus dribbling down the wall past the edge of said pain, as we both know it will!

 

[EatenByLimestone]

Any way to run PEX up there and cut the water heater out entirely? It seems like it would be the best way to keep it from leaking would be to eliminate it.

 

[Ashful]

Any way to run PEX up there and cut the water heater out entirely? It seems like it would be the best way to keep it from leaking would be to eliminate it.

Not a bad thought, actually. They ran three pipes from basement to the third floor, one each hot and cold to the kitchenette, but then a separate cold to the bathroom, adjacent to this extra water heater. I can see three possible reasons for this:

1. Quicker hot water and less transit loss to the bathroom, as the run is quite long, easily over 60 feet.
2. Manage load on the basement water heater. The main water heater is supplying 2 showers + 13 sinks + 2 dishwashers + laundry, although being a boilermate, it seems to have pretty close to endless supply.
3. It was just too difficult to route two pipes up there.

I suspect reason 3 is why we have this setup, but will investigate. There would be a serious penalty in warm-up time for that shower and sink, but nothing worse than we have for some of the other more-distant sinks in the house. It would also not resolve the issue of having cold piping in an un-conditioned attic, although it may be possible to reconfigure that piping close to the wall and play the game of framing out the wall to insulate around it.

 

[zrock]

That pan under the tank is code in most places except they should not have put that pipe on it.. If it were me i would be getting rid of the upstairs tank. No matter how carful you are and how well you think you are prepared if things go bad all that water has to go somewhere and that is down.. the expense of moving it now could save you huge if you ever had a unforceen failure. Not to mention i could not sleep at night knowing i had hot water above my head..LOL..

 

[begreen]

15 yrs. on the water heater is definitely pushing it. Is that really a 60-gallon water heater? For one bathroom a 20-gallon unit with quick recovery would suffice. A smaller unit may also stop guests and daughters from taking forever showers.

It sounds like a small on-demand system will solve a lot of concerns. Note that eventually, it too may leak, but will not have a huge reservoir attached.

 

[stoveliker]

Other than the volume of the water grid...?

 

[begreen]

Other than the volume of the water grid...?

At that point, it's the same issue as with any plumbing leak depending on the size and duration. We had a pinhole leak in the flex lines connecting our hot water heater in the pit basement several years ago. It wasn't a flood, but under pressure, it sprayed a lot of water over many cardboard boxes and was a pita to clean up.

Then, a year ago we had a pinhole leak form in a copper elbow, that was buried in a cabinet wall. That was lovely to fix. I posted that fiasco earlier. There are some things one can not predict.

 

[stoveliker]

I agree. That is why I think reservoir or on demand doesn't make a big difference. Even if the reservoir springs a leak, it's automatically filling up from the water grid. A leak never stops until it's found and fixed, regardless of the nature of the system.

 

[ABMax24]

Navien tankless units also have freeze protection.

I have one, it has a built in circulator with "intelligent preheating" that learns usage patterns so at common times hot water at the taps is only a few seconds away.

In your case though I'd try to eliminate the heater in the attic entirely and pull hot water from somewhere else, especially if you could add a circulator.

As an aside: It just boggles my mind that a house from the 1770's is still habitable. Your house would have been 140 years old before our city had it's first house (and it would have been about 12ft x 16ft in size).

 

[stoveliker]

That is because of the building materials. I see a lot of stone in the pics. And have seen big beams earlier.

I went to college in a town with 250 year older homes than that. Again, stone (brick in that case, but also quarried sandstone).

 

[Ashful]

No matter how carful you are and how well you think you are prepared if things go bad all that water has to go somewhere and that is down.. the expense of moving it now could save you huge if you ever had a unforceen failure.

Well, any leak in any plumbing up there is going down, no difference there. I've had two friends homes wiped out by plumbing failures in the last few years, both were failed hoses (one washer, one toilet) than ran full-bore undetected for probably 8 - 10 hours while the home was empty. No tank involved.

Not to mention i could not sleep at night knowing i had hot water above my head..LOL..

It's over my son's room, but thankfully not over his bed. The larger concern would be the office full of computing hardware below that, upon which my livelihood presently relies, as water will travel.

15 yrs. on the water heater is definitely pushing it. Is that really a 60-gallon water heater? For one bathroom a 20-gallon unit with quick recovery would suffice. A smaller unit may also stop guests and daughters from taking forever showers.

Sorry, I did make mention of a 60 gallon can somewhere above, but did not mean to imply this one was that size. I believe this is probably only 30 or 40 gallons. It's a good size, in that at least three of us can get quick showers, esp. if we make the teen go last. We had to test that last week, while getting the oil tank changed on our boiler.

It sounds like a small on-demand system will solve a lot of concerns. Note that eventually, it too may leak, but will not have a huge reservoir attached.

Other than the volume of the water grid...?

I've been putting thought into this. I have a Fortrezz Z-wave valve rigged thru my alarm panel, to shut down the entire house if a leak is detected. I have leak sensors installed in the room adjacent to my basement boiler room, behind our washer (hoses), and one in the drip pan on this water heater. If any of them get wet, the water to the whole house shuts down, all of our phones will wail at us, an the lights go on everywhere in the house.

The trouble is, as begreen properly noted, there's 30 or 40 gallons of water stored in that tank. I believe most water heater leaks start as a slow weeping, something easily caught with a rag or sponge, while you figure out how to get the system safely drained. In fact, if they hadn't stupidly buried the drain cock, I'd just attach a garden hose to that and feed it around the corner to the shower drain.

But with a tankless, the likelihood of an undetected leak seems much higher. These things don't sit in a pan, and it's almost certain any leak is going to just dribble down one of the pipes (or wiring), to some un-predictable location, where the water sensor will not as quickly detect it. For this reason, and because of the potential for freezing, I'm starting to lean back toward a new tank of similar size and type, but installed with a few improvements:

1. Proper access to drain cock.
2. Install over drip pan (likely larger than this one), with flood sensor installed.
3. Install on unions (maybe even PEX) for easier future replacement.
4. Write a date on the thing, set a calendar reminder, and just replace it every 10 years.

Navien tankless units also have freeze protection.

Good to know. So do Rheem and Rinnai, if you want to go with a gas setup, but I had found no all-electric options with freeze protection. I did check directly with Stiebel Eltron technical sales, and none of the several all-electric brands they make contain freeze protection.

As an aside: It just boggles my mind that a house from the 1770's is still habitable. Your house would have been 140 years old before our city had it's first house (and it would have been about 12ft x 16ft in size).

It's all relative, I guess. They have older homes in Europe, although they tend to heavily renovate them, most often essentially building a new home in an old shell. Even my European friends are always amazed by the way we tend to keep our old windows, doors, and floors.

I've spent my life in and around old houses, my family having settled the area where I grew up in the late 1600's, and many of the original homes just passed down thru the generations. The most troublesome ones (to me) have been those built when plumbing and electrification were new (eg. Victorian), as they were plumbed and electrified with some horrifying technology. Most of these Revolutionary-era farm houses were too remote to be electrified and plumbed until closer to WW2, and thus received much better tech, not that I love touching now-80 year old wiring.

 

[brenndatomu]

There would be a serious penalty in warm-up time for that shower and sink, but nothing worse than we have for some of the other more-distant sinks in the house

They make valves that will use the cold water line to circulate the water until the hot water gets to the fixture...might be an option if you remove the attic water heater?
Edit: it's called a D'Mand kit
Faucet Depot
https://www.faucetdepot.com › man
ACT D'MAND Kontrols Systems - Recirculator Pumps

 

[mellow]

Have you pulled the anode rod on that water heater to see how it is doing?

Other thing is look at 110v on demand made for RV's or you could put 30 gallon propane tank in the bathroom and run a ventless HWH.

 

[Ashful]

Have you pulled the anode rod on that water heater to see how it is doing?

Other thing is look at 110v on demand made for RV's or you could put 30 gallon propane tank in the bathroom and run a ventless HWH.

I have not. After this many years, and knowing how little attention the prior owners paid to water quality, I’m frankly afraid to touch it without having its replacement sitting here ready to install.

I have propane here, 500 gallons buried in the yard with regulator and manifold mounted right below this attic window (well, 50 feet below), so it’d be easy to get propane up here. But venting would be a challenge, and I have a very strong bias against ventless. For this reason, I’m favoring electric.

Wondering if this might be a place to play with a hybrid ASHP water heater. Sure, it’d go resistive much of winter, but this attic roasts under a raised seam metal roof every sunny day for most of the year. Also, many of them have stainless tanks, so even if I’m not saving much on operating costs, I’d hopefully have something less prone to leak?

The major stroke against hybrids would be the vibration, being mounted above most of our bedrooms. Also, how do the ASHP refrigerant loops hold up to attic temps, that may swing -10F to +140F?

 

[stoveliker]

And where do you drain the condensation from the ashp (in summer)?

 

[EbS-P]

I have not. After this many years, and knowing how little attention the prior owners paid to water quality, I’m frankly afraid to touch it without having its replacement sitting here ready to install.

I have propane here, 500 gallons buried in the yard with regulator and manifold mounted right below this attic window (well, 50 feet below), so it’d be easy to get propane up here. But venting would be a challenge, and I have a very strong bias against ventless. For this reason, I’m favoring electric.

Wondering if this might be a place to play with a hybrid ASHP water heater. Sure, it’d go resistive much of winter, but this attic roasts under a raised seam metal roof every sunny day for most of the year. Also, many of them have stainless tanks, so even if I’m not saving much on operating costs, I’d hopefully have something less prone to leak?

The major stroke against hybrids would be the vibration, being mounted above most of our bedrooms. Also, how do the ASHP refrigerant loops hold up to attic temps, that may swing -10F to +140F?

Over kill for a bathroom. IMO. Would unlikely see ROI in the units lifetime. From the manuals I read they really don’t want them installed placed that get that cold. Condensate drain will likely plug at some point. Hi water cut out would then just kick it into resistive mode. And you’d need to get the alert via some app that it’s switched over due to high water.

I think you may be overthinking here. I just don’t see how things could get simpler than a 2.5 gpm on demand electric. All ready have 40 amp wiring there for the old one.

 

[Ashful]

I think you may be overthinking here. I just don’t see how things could get simpler than a 2.5 gpm on demand electric. All ready have 40 amp wiring there for the old one.

All good points above. But given the freezing issues, and the fact that the present tank unit pulls way less than 40 amps (and most recommended tankless were actually 60A or higher), I disagree that tankless is the easiest solution. The simplest thing would be to just replace what I have with another identical unit, which has the benefit of offering probably a few days' freeze protection to all connected piping, in the event a winter storm knocks out our power (not completely uncommon). Arguments could be made for just draining down the tankless system in that event, but that would require me being here, which isn't always the case.

Tankless does have some benefits, namely lower energy usage when there's very little water usage, and the lack of stored water. But it really does appear the disadvantages outweigh the advantages, in this case.

It's looking like the top contenders are either simple replacement (with better setup for draining), or re-plumbing to just pull directly from the boilermate. Given that re-plumbing would likely require tearing up some floors and walls installed after those lines were run, it's very likely I'm going to just stick a new electric tank up there, with plans for more frequent replacement.

 

[mellow]

I have my HPWH in my unheated garage, I insulated my water lines going to it, does just fine in the winter. The previous WH was in the same location for 20 years.

 

[Ashful]

I have my HPWH in my unheated garage, I insulated my water lines going to it, does just fine in the winter. The previous WH was in the same location for 20 years.

Yeah, I agree it could be made to work, but there are some good arguments that make it less favorable in my case:

1. Usage is extremely low, zero to negative ROI. I think we have averaged less than 20 gallons per YEAR thru this water heater, the last 10-12 years. That will rise if a teen boy moves into this suite, but even still... it's just one shower + sink.

2. Present drain exits thru soffit to gutter, then downspout. There will be undoubtedly be sunny but cold winter days when attic is warm enough to trigger HP mode, but pipe exiting soffit is cold enough to freeze and plug.

3. Our average and record winter lows are about 6°F below yours, which isn't enormous, but may be a factor if it puts us on either side of an operating threshold.

4. Vibration, I really don't want to listen to a compressor running overhead, and electric WH's are nearly silent.