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Thread: Holy Cow! Now that Prices have changed, Which Way Should I Proceed?

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    DIY Junior Member DEDon's Avatar
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    Default Holy Cow! Now that Prices have changed, Which Way Should I Proceed?

    I came here, last year and decided to wait until my 19 YO A.O.Smith actually fails. After a thorough tank flush and although the thermostat is all the way up to the limit, it still hasn't failed. I have a power vented unit in the basement and, after replacing the leaking pressure valve and doing a flush, it has no leaks and has enough hot water for two showers.
    I had shopped around the Net, last year, and had pretty much decided on another power vented unit from A.O.Smith. Of course, since I had to trash my old hard drive on the computer, I lost all of that information.
    I know that I do want a high efficiency power vent unit and NOT a tank-less unit.
    I surely would like to do this job myself so I may ask about the gas plumbing changes that are needed, if any in fact are needed. My hope is to find a new unit that matches up to the old unit in exterior dimensions and plumbing dimensions, as well, so that there will be little to do but shut off the gas, evacuate the plumbing, disconnect, connect the new and turn it on and fire it up. It shouldn't be THAT big a deal. Right?
    My current unit is a FPS--40--J00N010000, a 42K BTU Gas fired unit.
    I would like to move up to a larger volume unit, even there are only two of us living here.
    I'm open to suggestions and providing any additional information.
    While at Costco the other day, I noticed a Lenox Promo table and asked for literature. I haven't called for an estimate appointment because I would like to do this on my own or with a helper. Any suggestions or comments?
    Is it practical to consider more for a Hybrid or High Efficiency Unit, considering the relatively small amount of savings that I will realize by doing so?
    Thank you.

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    In the trades Dana's Avatar
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    Do you need a bigger tank for the tub-filling capacity, or is it a running short on shower-water kind of deal?

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    DIY Junior Member DEDon's Avatar
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    Dana, thanks (a few months late)for the reply. I do need a bigger tank. The showers water doesn't stay hot, very long. I'm still using the old heater and it is getting closer to upgrade time (unit is just shy of 20 years old, now). The temperature setting on the unit is up all the way.
    Now, I have two more, living here. We're probably stressing the unit.

    It appears that I am going to have to go to another power vented unit because of location in the basement.

    I've been looking at A.O.Smith's 50gal Power Vented Unit. May I ask you for some suggestions, please?

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    Retired Defense Industry Engineer jadnashua's Avatar
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    What Dana was leading up to, was, if you have the room, a waste water heat recovery system could save the cost of a larger unit, and provide longer showers with the same sized unit. It has no effect when you're trying to fill a big tub, since there's no warm water going down the drain at that time. Rather than repeat all of that info, just do a search, it's been discussed a lot here. Also, assuming your prior thread was on this forum, it may easily still be here...the search function again to the rescue.

    In gas-fired WH, the two companies that seem to get the most stars are Bradford-White (you may have trouble buying one of these as they want it installed right, and tend to only sell to plumbers) and Rheem.

    The overall size of the units is likely going to be different, even for the same volume WH. The Feds mandated a vapor protection system for the burner that prevents it from igniting volatile gasses that may be in the area - gasoline fumes, solvents, etc. This typically has made the tanks somewhat taller. This may not be a huge problem IF your local codes allow flexible connections for the gas and water, the rigid connections almost never would line up.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    In the trades Dana's Avatar
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    Quote Originally Posted by DEDon View Post
    Dana, thanks (a few months late)for the reply. I do need a bigger tank. The showers water doesn't stay hot, very long. I'm still using the old heater and it is getting closer to upgrade time (unit is just shy of 20 years old, now). The temperature setting on the unit is up all the way.
    Now, I have two more, living here. We're probably stressing the unit.

    It appears that I am going to have to go to another power vented unit because of location in the basement.

    I've been looking at A.O.Smith's 50gal Power Vented Unit. May I ask you for some suggestions, please?

    It's highly likely that the reason you aren't getting the anticipated shower times out of the existing unit is that the dip-tube feeding the incoming cold water to the bottom of the tank has corroded and gotten much shorter, mixing the cold with the hot at mid-tank or higher. While this is a replacable part, it's not worth fixing a 20 year old hot water heater.

    Jim has it right- with a drainwater heat exchanger and a 42KBTU/hr 80% efficiency burner you can get "endless shower" performance during the summer/fall when the incoming water temps are warmer, and more than double the apparent-capacity of the tank during the winters. What you don't get out of it is "endless tub fill" performance, since to deliver the heat from the drain flow to the incoming water both the drain & hot water need to be running at the same time.



    If you upgraded to the condensing Vertex you'd have both a bigger burner, and more volume, but whether the upcharge would pay for itself in efficiency over hte anticipated lifecycle of the unit depends a bit on how much hot water you use, and your fuel costs. If you're on a natural gas main it might take a pretty sharp accounting pencil to figure that out, but if you're using propane it's a no-brainer- go for a condensing unit AND drainwater heat recovery.

    Drainwater heat recovery enhances the apparent efficiency as well as capacity, since it's taking heat that was literally going down the drain and returning it to the hot water tank. If you just swap out your existing unit with a comparable non-condensing unit and still don't have enough showering capacity, a drainwater heat exchanger will fix that. I suspect that with a shiny new unit that has a full-length dip-tube you'll be fine on showering capacity for a decade at least. At current natural gas prices drainwater heat recovery would probably take nearly a decade to pay for itself, but if it bumps north of $1.50/therm- delivered there's a reasonably short-term ROI on them. (If it keeps you from having to hear about it if your partner takes a shower right after you, the payoff is immediate! :-) )

    If you are heating your home with a hydronic boiler it may make more sense to install an indirect-fired hot water tank operated as a heating zone off the boiler instead of installing a standalone tank of any type. (It depends a bit on the boiler.)

  6. #6
    Master Plumber master plumber mark's Avatar
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    Cool Just want some information about this

    [

    Jim has it right- with a drainwater heat exchanger and a 42KBTU/hr 80% efficiency burner you can get "endless shower" performance during the summer/fall when the incoming water temps are warmer, and more than double the apparent-capacity of the tank during the winters. What you don't get out of it is "endless tub fill" performance, since to deliver the heat from the drain flow to the incoming water both the drain & hot water need to be running at the same time.



    Drainwater heat recovery enhances the apparent efficiency as well as capacity, since it's taking heat that was literally going down the drain and returning it to the hot water tank. If you just swap out your existing unit with a comparable non-condensing unit and still don't have enough showering capacity, a drainwater heat exchanger will fix that. I suspect that with a shiny new unit that has a full-length dip-tube you'll be fine on showering capacity for a decade at least. At current natural gas prices drainwater heat recovery would probably take nearly a decade to pay for itself, but if it bumps north of $1.50/therm- delivered there's a reasonably short-term ROI on them. (If it keeps you from having to hear about it if your partner takes a shower right after you, the payoff is immediate! :-) )


    Ok, I need to hear more about this drain water heat exchanger and what benefits it
    could provide....
    I read the link and it appears rather like something I dreamed up about 30 years ago... but never attempted because I could not see any payback or benefit...

    Why not loop some copper around the flu pipe on the water heater or on the furnace flu??

    better yet... Why not install a 30 gallon pre heating naked tank next to the heater..if you have the room.


    from what this fellow has presently, he probably ought to just get himself a
    50 gallon power vent and that will probably solve all his hot water problems without
    trying to break the bank... the extra 10 gallons is not gonna cost him but a few dollars a month more to heat and it will make the wife happy too......

  7. #7
    Master Plumber Caduceus's Avatar
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    RE: Drainwater heat exchanger.
    I would be surprised to see if this method of heat recovery has been approved by any plumbing code authorities. Though it is promoted by state and federal entities as a great 'green' resource, my understanding is that health departments and code enforcement agencies have not looked favorably towards them for a number of reasons.

    The main concern that I can see with this design is that a potable water supply pipe is in direct contact with a sanitary drain. This is a major plumbing 101 no-no. Both are made of a quality copper, but if ever there was a compromise between the pipes you would have a cross contamination problem. A variety of factors in any home in America could contribute to premature corrosion of the interior pipe walls and the 'human' factor must be recognized.

    Also, looking at the cost of the product and assuming it is installed as a DIY project to save money, I would think that your supply and drainage piping would have to be in an ideal design to keep the system efficient. If you have multiple stacks on different floors a lot of repiping and insulating may be required and a plumber would increase the costs.
    I have also looked at the cost recovery analysis for home owners and they seem to be over inflated. The same thing happened with tankless water heaters (and still is happening) where perfect lab environments didn't mimic real-life application and an inaccurate final analysis mislead the public. Tankless units were first said to show energy savings to recoup cost of installation in 5-7 years, now it is discovered that it may take 20-30 years to recoup the cost and the units typically don't last over ten years...can the same be said for drainwater heat exchanger systems? I don't know, but the green movement seems to love them and I guess time will tell.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    I can't see how there's any direct contact with the drain in them! You have two metal layers, the interior of the drain pipe is continuous, then the potable water supply pipe(s) wrapped around it, and they themselves fully self contained.

    FWIW, the state of Massachusetts is really fussy about what plumbing products are allowed there, and there are some of this type of fixture approved http://license.reg.state.ma.us/pubLi...overy&psize=50

    Now, whether the payback period makes it viable depends on your energy costs. It's a one-time installation, and should never need to be replaced.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Master Plumber Caduceus's Avatar
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    Quote Originally Posted by jadnashua View Post
    I can't see how there's any direct contact with the drain in them! You have two metal layers, the interior of the drain pipe is continuous, then the potable water supply pipe(s) wrapped around it, and they themselves fully self contained.

    FWIW, the state of Massachusetts is really fussy about what plumbing products are allowed there, and there are some of this type of fixture approved http://license.reg.state.ma.us/pubLi...overy&psize=50

    Now, whether the payback period makes it viable depends on your energy costs. It's a one-time installation, and should never need to be replaced.
    Yes, that's exactly what I said "potable water supply pipe is in direct contact with a sanitary drain." and you said the same thing, but different words "the potable water supply pipe(s) wrapped around it" which means that the water supply pipe is in contact with the soil drain. The pipes touch each other, right? The majority of plumbing codes do not allow such designs.
    As I stated before " if ever there was a compromise between the pipes you would have a cross contamination problem." meaning that if a pinhole corroded through the soil stack into the water line (or vice versa) the waste water would be exposed to potable water and create a cross contamination. Especially when dealing with metal piping on supply and waste lines(even copper to copper), they should never come in contact with each other. Avoiding the type of scenario that they have intentionally created, is common plumbing practice around the world.
    Also, when you said "It's a one-time installation, and should never need to be replaced." maybe you didn't know that it has a 10 year limited warranty. Why not have a 20 year or lifetime warranty? Because it could fail after 10 years and what could that failure include? Maybe pinholes and leakage between the pipes? Who knows, but will the manufacturer tell us? probably not.
    Last edited by Caduceus; 11-04-2013 at 04:02 PM.

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    Master Plumber Caduceus's Avatar
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    Look, I'm not trying to turn this into another one of those endless sessions of eff-you and eff-you, too. I'm just stating concerns that I would have in the design and I found that others online have also. Most websites (promoted by manufacturers) will state "decreased risk of cross-contamination." but "decreased risk" doesn't mean "no risk", because that would be a bold claim. Every plumber out there who's worth a lick of salt will tell you that pinholes occur, pipes shouldn't contact or support each other and proper precautions should always be taken to avoid cross contamination. That's all. I also found a site that Dana has also commented on, where an inspector didn't approve the installation. He was probably looking into the best interests of the public health and not at profits or saings. He probably was thinking the same thing as myself and others who have commented on the product. You can try to swirl a cloud of logic around it and justify it's existence with ASTM numbers and UL listings, but the very simple basics of plumbing are always there for a reason and if you wanna play guinea pig for new technology, go ahead. There were a lot of products that spent years on the market 'approved' until it was discovered that they were hazardous. It only takes one time for something bad to happen and you always believe it won't happen to you...until it does.
    Last edited by Caduceus; 11-04-2013 at 03:18 PM.

  11. #11
    Master Plumber master plumber mark's Avatar
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    Quote Originally Posted by Caduceus View Post
    RE: Drainwater heat exchanger.
    I would be surprised to see if this method of heat recovery has been approved by any plumbing code authorities. Though it is promoted by state and federal entities as a great 'green' resource, my understanding is that health departments and code enforcement agencies have not looked favorably towards them for a number of reasons.

    The main concern that I can see with this design is that a potable water supply pipe is in direct contact with a sanitary drain. This is a major plumbing 101 no-no. Both are made of a quality copper, but if ever there was a compromise between the pipes you would have a cross contamination problem. A variety of factors in any home in America could contribute to premature corrosion of the interior pipe walls and the 'human' factor must be recognized.

    Also, looking at the cost of the product and assuming it is installed as a DIY project to save money, I would think that your supply and drainage piping would have to be in an ideal design to keep the system efficient. If you have multiple stacks on different floors a lot of repiping and insulating may be required and a plumber would increase the costs.
    I have also looked at the cost recovery analysis for home owners and they seem to be over inflated. The same thing happened with tankless water heaters (and still is happening) where perfect lab environments didn't mimic real-life application and an inaccurate final analysis mislead the public. Tankless units were first said to show energy savings to recoup cost of installation in 5-7 years, now it is discovered that it may take 20-30 years to recoup the cost and the units typically don't last over ten years...can the same be said for drainwater heat exchanger systems? I don't know, but the green movement seems to love them and I guess time will tell.
    Ditto to everything you say here...
    I think that this product is probably totally worthless..
    and there could be issues with some sort of cross -contanimation...

    in most cases if you put a coil around a copper stack, some day
    something from above is gonna let loose and the whole pipe will
    be covered in crap... including the potable water coil....

    I would much rather just strip a 30 gallon good used water tank and
    set it next to the water heater for heat recovery...

    if you want to get really thrifty, why not put a bypass on the system
    and run a 400 foot coil of aquapex pipe up in the attic and collect the
    heat in the summer time?? and drain it down in the winter??

    I would consider doing that If I wanted to pinch a penny,
    but I am a plumber and got
    plenty of money, so I wont bother......



  12. #12
    In the trades Dana's Avatar
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    Yep they're completely useless, which is why after round after round of third party testing & developing functional models the Canadian government is subsidizing them, as are a handful of US states and several utilities- they're all just in it to soak the ratepayer/taxpayers.

    Drainwater heat recovery is one of several a water heating techologies getting a second look by the US DOE, based on the Canadian success. Not sure if/when they will be publishing any analysis. The vendors have paid for their own financial analyses of different water use & utility cost scenarios for some US markets, including northern Minnesota, where the incoming water is cold, tending to favor drainwater heat recovery, but the electricity is cheap, tending to dis-favor it.

    And you should never put potable water in any building or plumbing chase that also has sanitary drains, since there is a chance that when drain fails you could get germy stuff on the outside of a potable line.

    Where inspectors have dis-allowed the installation it pertained to a particular line that uses heavier tubing that was too large to be tested under ASTM B88, and was thus not marked with the potable-stripe. This has been looked at by state regulatory bodies in multiple states that DO allow (or subsidize) drainwater heat recovery on potable systems, and it has passed muster. (This is true in MA where that model line is the ONLY drainwater heat recovery units currently on the pre-approved plumbing fixture list.)

    The thread discussing where it was disallowed by a pointy-nosed inspector lives here. The rejection by the inspector clearly had nothing to do with the potable-next-to-sanitary-drain construction, only the ASTM B88 issue.

    Other vendors use only ASTM B88 tested tubing, which works because they are not brazing manifolds on the potable side to split the flow into multiple sections to limit the pressure drop. Only the one vendor (Renewability) is affected. Competitors have in the past tried to make hay on that issue to cut into Renewability's market share, which is substantial. In Canada Renwability's PowerPipe series is distributed & retailed by both Home Depot and Sears, as well as a handful of smaller vendors. In the US they are retailed through Home Depot and a very few smaller companies, but also wholesaled by EFI.

    US D.O.E. testing on the earliest version of potable water gravity film drainwater heat exchangers starting in the early 1980s (these things have been around since President Reagan's first term) estimate a ~40 year lifecycle before the return efficiency has degraded to 75% of it's day-1 effectiveness.

    Bottom line, it's not going to save most people heating hot water in a 40-50 gallon gas hot water heater enough to make it an exciting investment (though it still has an ample lifecycle payout, even for gas-burners at current pricing.) For those using more expensive fuel it has a very reasonable IRR and NPV. But it can more than pay for itself right up-front in applications where the showering use is large enough that the load can't otherwise be met without significantly up-sizing the hot water heating system.

    The pin-hole leak corroding though the copper drain to the potable resulting in an ongoing contamination of the potable is not a likely scenario. It's a friction-fit between the copper pipe and the potable, and if/when a pinhole develops in the potable, the leaking water would be all over the exterior of the heat exchanger, making itself known. (Whether that's the "...cloud of logic..." spun by the state regulators that explicitly allow them is unknown to me.) But if you have acidic potable water funky grounding issues with the electrical system bleeding parasitic current through the plumbing sure, there's always some theoretical chance of cross contamination, but if that's been happening, the bodies haven't shown up yet and there are real numbers of them out there 30+ years after the first ones were installed.

    If as stated "The majority of plumbing codes do not allow such designs.", please point us to the relevant language in the IPC.

    A tempering tank next to the hot water tank is not a heat recovery system- it's a parasitic load on the heating system. In cooling dominated climates it may make sense though. But it also takes space, which is often at a premium. Using the attic as a drain-down unglazed solar collector kinda-works, but the complexity of design & installation of a system that actually passes muster with the IBC is a bit more than drainwater heat recovery, and the return likely less (depends on just how your design is.)

    The heat exchanger doesn't have to be right next to the hot water heater or shower (any more than the hot water heater needs to be next to the drain or shower), though it's more convenient if the runs are short. The tepid- water output of the heat exchanger loses very little heat along longer plumbing paths because it's very close to room temperature.
    Last edited by Dana; 11-05-2013 at 08:00 AM. Reason: fixing links, spelling

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    Master Plumber Caduceus's Avatar
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    Y'know Dana, if you actually had any real world experience in plumbing and had to go into peoples homes on a daily basis and see the problems that occur and have to find a safe and sound solution, you may actually see what we are talking about. But you don't and never have had to experience the type of accountability that plumbers have. Just like state and federal approval committees, every body looks at the stats and doesn't consider potential negatives until something bad happens...then it turns into a blame game about who's fault it is. And you know who usually discovers these problems? The smaller local jurisdictions that have the public interests as a priority. You are way off base with your sarcasm because it shows that you have absolutely no understanding of the most simple of plumbing installations. You just recycle and spout out what other people have already said and any independent thoughts are soaked with inexperience and lack of true knowledge that a 2nd year apprentice would laugh at your naivete. Your knowledge of cross contamination hazards should be kept inside your head and away from public exposure.
    By the way, water cooling drinking fountains had the same design on their drains years ago where the copper supply coiled the drain tailpiece, but after they were on the market it was discovered that the pipes would corrode and allow draining water to come in contact with the supply water. I actually removed one about a year ago and the weeping water going into the drain could barely be heard, but it was still a cross contamination hazard...y'know, the real life kind that really happens in the real world. Did anybody become sick because of it? I don't know, but chances are if anybody did they trusted to be safe in public and probably would never suspect it. Maybe blamed it on dining out, like so many people do.
    It is this simple, no matter what any governing agency approves, copper drains and copper water supply pipes shall not contact each other or be supported on each other...ever...period. If you have so much freakin' time on your hands to research these products then take some of that time and research the plumbing codes and find the sections yourself. I'm not teaching a plumbing code class to somebody who doesn't or can't listen to the basics to start with, so it's pointless. I'm sure years ago you would have defended asbestos as the savior of the construction industry and cited many proven studies as to how wonderful it is. Is it possible that manufacturers of asbestos materials were in cahoots with the government...maybe. Maybe the same is true for drainwater heat recovery system manufacturers...THE CONSPIRACIES NEVER END!! OH, NOOOOOO! Maybe YOU have a financial interest in them. Hmmmm, sound like familiar accusations?? Maybe read some other posts throughout the forum to refresh your memory.
    What is it that you have actually done in relation to this type of work that makes you so skilled at assessing its usefulness or safe application in a home? Well? Do you even understand what you are defending? It doesn't sound like you do.
    Seriously, just shut up sometimes. Your banter makes you sound really dumb...even to us dumb plumbers.
    Last edited by Caduceus; 11-05-2013 at 10:12 AM.

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    Jack of all trades DonL's Avatar
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    Are we going to have a pissing contest ?

    If so I would like to get in on it.

    I still have good Pressure, Distance and Endurance.


    Can I play too ? Or should I just place my bets ?
    Theory only works perfect in a vacuum.

    Cyber Security Protection for Windows C:\ > WWW.WinForce.Net

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    In the trades Dana's Avatar
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    Quote Originally Posted by DonL View Post
    Are we going to have a pissing contest ?

    If so I would like to get in on it.

    I still have good Pressure, Distance and Endurance.


    Can I play too ? Or should I just place my bets ?
    No interest- sorry to disappoint.

    Hope there was enough info in those links to satisfy master plumber mark's curiosity.

    If not, using the private messaging on this site to stay out of the free-pissin' zone is fine.

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