Tankless vs waiting until my tank heater fails again

Discussion in 'Water Heater Forum, Tanks' started by mawg2u, Oct 29, 2009.

  1. mawg2u

    mawg2u Civil Engineer semi-retired

    Messages:
    3
    Location:
    Toronto
    Gents / Ladies

    I bought this old house in Toronto back in 1991. About 1995 the tank water heater started leaking and I had it replaced by the hydro system I rented it from. In 2005 the bottom fell out of this "new" tank and flooded my finished basement. What a mess. Insurance did paid for this and they've been duking it out with Toronto Hydro to this day to find fault.

    In the rush to get my basement and plumbing working, I bought a tank and had it installed in a day or so. I'm now watching the clock and don't plan to wait a full ten years before replacing this tank, but with what.

    A couple of days ago a guy knocked on the door touting tankless Navien or optional Rinnai. It would cost $38/per month going forward, installation included plus any wrinkles in the installation. I've been thinking seriously about this if only to avoid having my basement wiped out for several months when this tank does fail.

    I don't hug trees and I have the enough coin to not worry about when I reach payback. I'll be dead before then and my kids can enjoy the rest. I just don't want me or my kids facing the same hassles.

    I'm told that buying outright would cost about $3500 for the Navien and then I'd be on the hook for maintenance outside warranty. Ouch..!! I think renting is the better option.

    Ductwork to the outside is about three feet through a wall to the underside of my veranda so this SS cost issue isn't big. I just want to know what is the most reliable system to go with, Navien, Rinnai, Takagi, Paloma, Bosch or whatever else is out there. Noise would be an issue as well. I'm told Navien has worked some of their bugs out in the last few months but who knows.

    I would appreciate any thoughts on this.
    Last edited: Oct 29, 2009
  2. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,360
    Location:
    Yakima WA
    The troops are quite polarized on the question of tank vs tankless water heaters. The tankless crowd argues economy, space saving, and never ending hot water. The rest of us point out the studies showing the very high cost of the tankless units, high cost of installation, high cost and frequency of necessary cleaning, the fact that in cold weather, you do not have the abundance of hot water claimed, and the need of increased electrically supply or larger gas mains in the cases of retro fitting. Studies show pretty conclusive evidence that tankless are more expensive in the long term. It is very unusual for a conventional water heater to just suddenly fall apart. When the tank begins to fail, is shows up in small leaks that do not result in an immediate flood. These studies show you can operate and replace a conventional water heater 3 or more times for the cost of a tankless with all factors considered. Tank life seems to depend a great deal on the quality of the water begin heated. Some areas have water that will destroy a tank in a few years while other places the tanks will last for many years beyond their life expectancy. My advice is to study both sides of this issue very carefully before plunging into the tankless.
  3. Dana

    Dana In the trades

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    OK, I'm callin' ya on it: Show me the studies!

    (And if you pull out that silly Consumer Reports hack job I think I'll laugh myself silly! :) )

    The costs & benefits will vary dramatically by how you use water, and what your fuel rates are.

    Still, if you have a new tank, $38CDN/month is a lot of freight to pay for the appliance, even if installation & maintenance IS included (and I wouldn't touch it if all maintenance is yours, at that rate!) You can boost the performance of the tank considerably by insulating all of the near-tank plumbing and giving it an overwrap of R10+, and insulating the HW distribution plumbing where ever it's accessible. With tanks it's all about reducing standby loss- the combustion efficiency is nearly 80% for all of 'em, but the standby losses kill. With tankless units it's all about cycling-efficiency- short draws are atrociously inefficient, and they only make it up for long draws like baths & showers. A 0.82EF tankless usually only performs a true 75% efficiency in real-world use. A well insulated tank with near-tank plumbing insulated takes it from 60% to 70% for the "average family", higher for huge volume users, but it'll be much much lower for low volume users.

    If you & your family are the showering types (not much for tub-bathing) and the layout is reasonable, in most of Canada you can trot down to the local home-improvement box store an buy yourself a drainwater heat exchanger, for under $1kCDN which will boost the average apparent-efficiency of a cheap tank into the true as-used tankless range. (It would boost a tankless into the apparent-efficiency of a condensing-tankless range.)

    Tankless units are great if you have big tubs to fill or you have 5 people taking showers in succession- you never really run out. The only time you'll feel it running short on capacity is with multiple simultaneous high-flow draws. Standby losses are zero. But they have their other quirks. I've never met anyone with a decent tankless who ever wanted to go back. But for $38/month it's worth putting a wrap on the tank and waiting at least 5 years. The maintenance issues are highly overstated. Unless you live in a hard-water location where it needs frequent de-scaling, they're not dramatically higher maintenance than tanks, and most of the maintenance is DIY-stuff.
  4. Runs with bison

    Runs with bison Member

    Messages:
    892
    Location:
    Midwest
    You could buy a new water heater every year at that rate (but then you would have to add install) so I don't think this option is particularly attractive.

    I vote "none of the above." $3500 is an awful lot of money to spend on a water heater, as is $38/month. The potential energy savings are about $100/year (about $8/month.)

    If one is particularly concerned about catastrophic failure then some sort of strategic positioned moisture alarm would make sense.

    On the other hand, if you want to go tankless I believe you can do it far more cheaply than $3500 purchased and installed, or $38/month rented.
  5. Dana

    Dana In the trades

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    Location:
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    OK, that looks like 2 votes for waiting for the tank to croak, or at least mellow with age a bit... :)


    Unless your local water pressure is unusually high or water particularly corrosive, a repeat of the catastrophic failure & flood is extremely unlikely- SO unlikely that I'd be happy to sell you insurance against that eventuality for a mere $25/month... :)

    Tankless units can fail catastrophically too, nothing's perfect.
  6. mawg2u

    mawg2u Civil Engineer semi-retired

    Messages:
    3
    Location:
    Toronto
    Thanks for the comments

    I agree that going tankless will hit me $ wise for sure. I'm only concerned with the tank unit failing again and wiping out my basement for another three months. Having to keep that in the back of my mind is a pain. Insurance covers the damage but not the grief. It's happened twice already, albeit the first time was caught before a disaster.

    I guess I'll just buy another standard tank in a couple of years and have done with it. Perhaps at some point this technology will be competitive. It sure isn't now.

    Thanks for the input.

    Robert
  7. Dana

    Dana In the trades

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    I forgot to ask how you're heating the place? If you have any form of hydronic (forced hot water), radiators/baseboard/radiant-floor the best way to go would be with a indirect-fired tank running off the boiler. It's cheaper & lower maintenance than a tankless, with similar annual efficiency, beating a standard tank on efficiency & longevity.

    If it's an old-skool cast-iron type boiler, going with buffer-tank type "reverse indirect" will improve the AFUE of the combined system considerably, since the thermal mass of the tank then prevents the boiler from experiencing efficiency-robbing short-cycles.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,153
    Location:
    New England
    In a finished basement, it is kind of bad news to not install a safety pan for the WH. On a gas WH, there are a few things you can do to help protect yourself. One is install safety valve www.wagsvalve.com. It will shut the water and gas off if it detects a leak. That's the reason for the pan...it needs to reach about 1/2" deep before the thing will shut the gas and water inlet off. THen, if it is in an area that is out of sight, you may want a moisture sensor alarm to alert you to the fact it has started to leak. It could leak a little bit for weeks before it accumulated enough to trip the wags valve with some evaporation and a slow leak/drip.
  9. mawg2u

    mawg2u Civil Engineer semi-retired

    Messages:
    3
    Location:
    Toronto
    Thanks again

    My place is forced air gas.

    I'll check out the options on a sensor to detect leaks and shut off valves for gas and water in combination.

    I don't need a tankless, just some comfort on the whether the tank is about to crap out on me. I'd also do not want to replace it years in advance just for the safety factor.

    Cheers and thanks for the advice.
    R
  10. how about a pan ???

    If you install a pan under the water heater, and pipe it to the nearest floor drain, usually that will avert most average disasters from flooding the basement...

    now....let me guess, you dont have a sump pump pit or a floor drain in the basement.....right??

    surely aafter that alst disaster and flooded basement, you have a pan under the water heater...right??

    they are like only 9 bucks

    please tell me you do...

    here is my information on tankless heaters

    38 bucks a month plus operateing costs seem a tad bit high..


    3500--4500 is about what they are installing them for in indy

    here is everything I know about tankless


    http://weilhammerplumbing.com/houseofhorrors/
    Last edited: Oct 30, 2009
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,835
    Location:
    Cave Creek, Arizona
    Dwhe

    $1,000.00 for a "drain water heat exchanger"? What a waste of money that would be. In the first place the amount of heat recovered is miniscule, and the second would be finding a spot where it was exposed to enough "hot water" to even get that much. The reports are from companies, such as Bradford White, which make both types of water heaters so they do not have an axe to grind either way.
  12. Dana

    Dana In the trades

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    Location:
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    In coldwater Canuckistan it's 50-75 therms/year- comparable to what you'd save going tankless, for less than half the difference in installed price between a tank and a tankless.

    And if you shop around (rather than goin' box-store retail) you can find something less than half the box-store pricing (all but the tallest/biggest are well under $1000CDN anyway but it takes at least a 4-footer to be worth bothering.)

    Do the math (or read the results of those who have):

    http://www.renewability.com/uploads/documents/en/analysis_dwhr_minnesota.pdf

    It's very strongly present-value-positive at $1K for those who heat water with electricity in New England, and 2x the presumed price cited in the above anlalysis. NPV+ for those with 0.60EF tanks in high gas-price areas too, but it's a squeaker (the crash in gas prices this year make it seem like a loser, but that's this year.)

    There's a handy online calculator where Canadians can plug in their location, water heating method & utility prices to grab a quick cost/benefit that used to live here:

    http://www.ceati.com/calculator/

    (Doesn't seem to be working on my machine today.)

    Show me the Bradford White financial analysis (or any other manufacturers' analysis), if said documents exist. If you're gonna cite "studies", I want sources, not allegations of sources, with no way to substantiate either the claims or assumptions.
  13. Runs with bison

    Runs with bison Member

    Messages:
    892
    Location:
    Midwest
    While I'm skeptical about how often their installation is geometrically feasible, I do not agree that DWHR would be a "waste of money" or that the heat recovery would be "miniscule."

    I've actually worked through some design details on these to get a feel for them and they do show promise for 3-4 occupant homes with 2.5 gpm showerheads and moderate length showers (10+ minutes/each per day.) But much of this comes down to details. It isn't something one can easily make a blanket statement about.

    In trying to do a design myself I was impressed that they had maximized heat transfer in the main stack pipe by doing a vertical falling film design. (I've done wiped film designs and such industrially so I appreciated the logic of this.) It also makes sense that they did an "equal flow" design to maximize heat recovery. Neither of these are obvious when one starts with the simplest case, but they fall out when you do the heat and material balance on both sides of the exchanger, and start considering the limiting side heat transfer coefficient.

    Practically, for my installation there are some major problems. First is that while we have 4 showering occupants, our showers average less than 10 minutes, and with only 1.5/1.6 gpm of flow. Second is that only one of the showers (used by two of us) is well situated for this sort of heat recovery. It might be possible to arrange it so that two of the three showers could be plumbed through this...but it would greatly increase installation cost.

    For me the potential savings are smaller than the worst case in Dana's link because, while my potential efficiency of recovery is not that bad, the total heating load is much smaller to begin with. Plus, I'm on gas which is less costly.

    On the other hand, I could probably fabricate the exchanger myself for a lot less than what they are charging. I've made smaller ones before from copper and stainless tubing. But the alterations to the drain stacks and rerouting the water supply would set me back considerably. For a new home this wouldn't be an issue, and the payout should be reasonable.
  14. I thought he was a salesman


    Thanks for the information on that skumbag....
    I always thought he had another reason to be
    so snotty to the plumbers who did not agree with him
    and cheering on Tankless water heaters.....

    of course this all went down a few years ago 2009, and I would be willing to bet that this guy
    has moved on because the Tax incentives have gone away....

    he probably has lost his ass and
    gone out of business by now being 2013.
  15. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,835
    Location:
    Cave Creek, Arizona
    The key to the original posting was that this was a "door to door" water heater salesman, (probably also sells water softeners under the same terms), which would ALWAYS be a "rip off".
  16. Dana

    Dana In the trades

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    Location:
    01609
    Thanks for the endorsement! :cool:

    Whether Dominic was just astroturfing for ThermoDrain or not, his initial posts had that appearance, and despite his wailing about being attacked he has neglected to actually deny it.

    My impression that it was astroturfing came from his stated comittment to buying from them, even after I pointed out where to get equal or higher performance products built by a competitor for substantially less money buying wholesale through EFI. His initial posting reads almost like an ad for Thermodrain as to why it is the better choice, his second posting dredged up long-since resolve ancient-history of an early manufacturing issue the competitor had experienced, and claimed that his choice was cheaper, despite EFIs published price list indicating the converse.

    Maybe he just didn't get it, or maybe he did and is simply so enamored of the product that it's worth spending the extra money to him for reasons unstated, beats me. But his charm offensive seems to have set some sort of record on this forum.
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