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Thread: Water Heater replacement as part of bathroom remodels

  1. #1
    DIY Junior Member Jdavis37's Avatar
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    Default Water Heater replacement as part of bathroom remodels

    First post and have read many other posts (thx to all) and learned enough to now want to know more. Later this year we are going to do complete remodels of our 2 upstairs bathrooms (close to full guts). My existing water heater (GE Box Store WH, 50 gallon NG) will be replaced. Currently, no mixing valves in the system and trying to find out if new code in NC requires or not (found article on line that said above 140 degrees a mixing code is required).

    Current water heater is old and has not had the suggested regular maintenance but even with that it has never produced enough hot water to fill the existing soaking tub which is not all that big. I am figuring on a replacement tub in the ballpark of 40-60 gallons (not huge but certainly larger than current). I enjoy a hot tub to relax my muscles at night and thus the desire for a HOT bath. Nothing worse than tepid water.

    My initial thoughts were to go tankless for the "endless supply of hot water". This remains an option. Downsides to this are:

    - Cost
    - long run from my gas meter to water heater (approx 35-40 feet)
    Tankless quirks unless I went with something along lines of an Eternal, etc

    Concerns with traditional tank water heater are somewhat obvious in that I do not want to have to do multiple fills on a tub. Tub size will probably be similar to this:

    http://www.jasoninternational.com/as...s/EM530_WS.pdf

    Not saying that particular model but just the size and capacity.

    Water heater currently is vented to roof using steel piping. Distance from water heater to both bathrooms is fairly short, master being longer of the two but still less than 25-30 feet max.

    After reading about mixing vsalves I am quite concerned about their effects on running water hot enough for my preferences. I understand the safety reasons and how they help even for simple things like a toilet flush during a shower but really dislike the side effects they can have, especially with tankless.

    Is it possible to fill such a tub with nicely hot water ( 104-110) using a tank based water heater. I am in North Carolina so winters here are fairly mild. Thx in advance, John

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    In the trades Dana's Avatar
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    Another downside to the tankless approach is the true fill time.

    In winter the incoming water temp in NC will be about 40-45F (depending on location), so you're looking at something like a ~65F temperature rise. With a 199KBTU/hr condensing gas heater you might get 195KBTU/hr out, which translates to (195,000/65=) 3,000lbs/hr, or 50lbs/minute, which is (50/8.34=) 6gpm. So for the 40-50 odd gallons you'll need it'would take about 7-8 minutes.

    With a tank heater your fill rates are limited by the impedance of the plumbing, and in most cases you'd get it done in something like 5 minutes provided you're using 3/4" plumbing both to and from the water heater.

    A 50 gallon condensing tank heater can get you there provided you have a big enough burner under it. The 50 gallon condensing Vertex comes in both a 76KBTU/hr (73K out) and a 100KBTU/hr (98K out)version. The 76K burner unit puts out 1200 BTU/minute, so with a 65F rise that's 18.5lbs or 2.2 gallons per minute, so during a 5 minute tub fill as the hottest water is leaving the top of the tank, it's capable making another 11 gallons of 110F water, but it won't be evenly distributed, it'll be mixing in with the water at the bottom, diluting the 140F water down by quite a bit. If you only needed 40 gallons of 110F water it would probably make it, but if you need the full 50, probably not. The 100KBTU/hr version would making about 15 gallons in 5 minutes, so if you started out with 140F water in the tank you should be able to get the tub filled in 5 minutes or less without the water at the tap dropping below 110F.

    Another downside to a tankless is the size of the gas plumbing necessary to get that many BTUs reliably to the burner, which in most houses would require 1-1/4" pipe (maybe 1" if it's less than 30' from the regulator with but a few ells). Depending on what other gas burners you have in the house, you may need to up-size the regulator too. The bigger-burner Vertex is still only half the size of the tankless, and if you're within 40' of the regulator you'd be able to use 3/4" gas plumbing. If it's looking too close, with a handful of ells you'd only need to upsize to 1". The 76K Vertex would be fine with 3/4" no matter what.


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    Retired Defense Industry Engineer jadnashua's Avatar
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    Where I live, regardless of how hot you set your WH tank to, you are required to install a tempering valve. Now, they come preset to 120-(maybe 119) degrees to meet the max 120-degree requirement for domestic use, but after the inspection, you could change it. But, it really doesn't matter, since in a tub, 140-degree water is too hot, and you'd be adding cold to it anyway, so it doesn't really matter if you do it before it gets there, or at the tub, and doing it before is MUCH safer. To keep from having to monitor the tub spout's outlet temp, I'd consider a thermostatically controlled valve - that way, it would automatically turn up the hot water to maintain the desired outlet temp until it reached all hot (and the tempering valve back at the WH would have done the same thing once it got below 120; i.e., no more tempering there).
    Jim DeBruycker
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    Master Plumber master plumber mark's Avatar
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    Why not just install a 75 gallon gas heater and it will do

    everything you will ever need it to do...... Many areas only
    require pressure balanced mixing valves at the tubs and showers...
    doing a tempering valve seems like its overkill in my opinion...



  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    The first time someone (it's usually the young or old who have the thinnest skin and get the worst of it) comes out with second degree burns because they didn't realize the water was so hot, you'll appreciate having a tempering valve at the tank! Or, even you, and you have something in your hand and you throw it away as a bad reaction. There's a reason codes are beginning to require them. Whether your locale does yet, expect it to in the future. Similar to requiring the antiscald valve. If it's not adjusted properly, you can get full hot out of it. Many people do not adjust the limiter since if done right in the summer, it may not produce hot enough water in the winter unless you adjust it again...another reason I like a thermostatically controlled valve.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member Jdavis37's Avatar
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    Thanks for the replies thus far. Giving me more to think through. Like every project I get into there is at some point a balancing point or in other words a good better best type thing, and trying to keep within a budget without going too crazy. As far as tempering valves, etc. I'll ensure I am following code (there will be a permit pulled for the remodels). If I am required to have such then time to research what affords best flexibility and convenience without penalizing us with tepid water.

    Based upon this input it would seem the most cost effective (speaking of installation costs only) would be something like this 75 gallon 76K BTU Bradford White water heater M-I-75S6BN. Am guessing this would fit into spot where existing water heater is just fine and assuming my current gas line is sized for it, no tmuch else to talk about.

    From there the solutions start to get a little more "involved". That said I am not opposed to such if it produces a better solution in the end. The AO Smith Vertex units I am guessing are all power vented. Price of the Vertex is about double that of the aforementioned BW 75 gallon heater plus installation will cost more. As a very rough ballpark gut feel, I am guessing the Vertex after installation will cost $1400 to $2000 more than the 75 gallon BW unit (given Vertex itself is about double BW price).

    Guess the obvious question is what does Vertex bring to table to justify nearly double the price of BW?

    While looking through AO Smith web site I ran across their "NEXT Hybrid" unit and wondered how this compares to tankless units such as the Eternal units. The "Next" is priced less than the Vertex and not having read about it in detail I have to assume it combines tankless technologies with some form of heat recovery built in. The "NEXT" is priced cheaper than the Vertex. Just not much information out there from actual owners and given that AO Smith on this forum is not exactly given stellar reviews by most/all it does make me wonder if this much technology in a water heater is worth the potential for hassles.

    My gut feel says I'll stay away from pure tankless unless I get a real push to go that way. Love thought of never running out of hot water but dislike thought of all potential issues. Vertex/NEXT Hybrid, others similar (Polaris seems quite pricey) may be worth considering though and of course the 75 gallon BW is perhaps thesafest and cheapest option! Thx again

    Quote Originally Posted by jadnashua View Post
    The first time someone (it's usually the young or old who have the thinnest skin and get the worst of it) comes out with second degree burns because they didn't realize the water was so hot, you'll appreciate having a tempering valve at the tank! Or, even you, and you have something in your hand and you throw it away as a bad reaction. There's a reason codes are beginning to require them. Whether your locale does yet, expect it to in the future. Similar to requiring the antiscald valve. If it's not adjusted properly, you can get full hot out of it. Many people do not adjust the limiter since if done right in the summer, it may not produce hot enough water in the winter unless you adjust it again...another reason I like a thermostatically controlled valve.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    FWIW, the tempering valve only adds cold to the outlet of the WH IF it is above what's left in the tank...IOW, if say the WH was set to 140, it would outlet 120-degree water until the tank cooled off to 120, then the tempering valve would stop adding cold. It would have no impact on making the water colder than it is set for.
    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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    In the trades Dana's Avatar
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    What the Vertex brings is 1/3 to 1/2 lower fuel use (depending on your total hot water volume use) than an atmospheric/power drafted 75 gallon unit, and a lower installed cost than a condensing tankess (with none of the quirks and fewer maintenance issues of a tankless. Depending on your water use & fuel costs (current and anticipated) the upcharge for a Vertex may or may not have a favorable net present value, but be sure to factor in any locale/state/federal subsidies you might get out of going with a condensing unit too. At even moderate volume hot water use a 95% condensing tank beats a 98% condensing tankless on fuel economy, since it never short-cycles. The only time the tankless beats it is on high volume use with mostly long draws. (The efficiency of any tankless on 0.5-2 gallon draws is pretty crummy.) From a "be nicer to the planet" point of view, lower fuel use is always better, of course, if the externalities beyond the IRR & NPV mean anything to you.

    The NEXT Hybrid won't cut it in this application, since it has only a 100KBTU/hr burner, and much lower storage volume than a 50 gallon tank- there's just no way to get to reasonable fill times on soaking tubs from here (you'd be better off with a 199KBTU/hr condensing tankless.) The biggest Eternal has a 195BTU/hr max, which comparable to a 199KBTU/hr condensing tankless, not better. It has fewer personality quirks, but the same maintenance issues of a tankless.

    What the Polaris brings is ~2x the anticipated lifecycle of a Vertex, primarily due to it's stainless steel construction. They are very comparable designs on the inside- you're paying for the stainless steel (which also has some scrap value after it's done.) Figure on getting at LEAST 20 years out of a Polaris, maybe even 30, compared to ~12-15 for the Vertex. The smallest-burner 50 gallon Polaris takes 130KBTU/hr-in, which is a significant up-sizing from a Vertex, which may effect fuel plumbing & regulator sizing, but it's enough to fill tubs that size.

    Both the Polaris & Vertex bring the potential for high-efficiency low-temp hydronic space heating to the table, if that's of any interest. Both are designed with ports already plumbed-in for combination hot water/space-heating applications, and it has way more burner than necessary for heating most houses, and is self-buffering- they can't short cycle on zone calls the way boilers can.

    Thermostatic mixing valves can go full-flow when the hot side input drops below the output setpoint- not all simple-minded tempering valves can, if you decide to bump up storage temps to 140F or beyond to get more capacity. (Basically, read the specs carefully when you buy.)

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    DIY Junior Member Jdavis37's Avatar
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    Dana,

    Thx.. I had looked albeit briefly at the polaris line up after seeing the Vertex and reading about some AO Smith woes (did not investigate the detail of the woes yet) as they seemed somewhat similar in nature. The Polaris is just getting over the top in terms of pricing for this remodel gauging by what the **** prices were. That said the Vertex models aren't exactly cheap either. I always try to weigh pros and cons during every remodel and have learned that there is a time and place to insist on the best and other places where one can go a different direction. Not sure about this just yet.

    The hybrid NEXT seemed at first glance a possibility with exception of the physical layout and now you've provided another reason to scratch it oiff the list .. thanks for that info.

    The 75 gallon BW has some nice advantages in that the tank cost is about a grand give or take, and if we are here 10 years from now (not sure about that) replacing it is fairly straightforward and affordable. Installation shouldn't be a night mare unless I need a larger gas line but even that is doable.

    The Eternal option is getting expensive especially when you include the installation assuming my gas setup will support a line that size. But it does offer a lot of hot water while minimizing some of the tankless issues. But keeps the scaling part to deal with and whenever it goes out replacement isn't cheap.

    Vertex 100K BTU 50 gallon heater is probably on outer edge of what my budget will support. We don't need any radiant heat from these guys, just hot water. Then add the power vent part of the installation etc. Trying not to talk prices on here but am guessing the Vertex with installation and Eternal will be close to same price give or take a little bit. The 75 gallon BW I am estimating to be about half the price of the other 2 options. Not really seeking payback (I had to tell the windows guy to stop trying to sell me on how much energy I would save but rather to tell me how they would never rot and never leak air!). In this case I want enough hot water that if I want a nice hot relaxing bath I don't have to run the tub half full, wait and repeat.

    The simplicity of the 75 gallon BW and cost is appealing. Not ruling out either of the other 2 options though it almost sounds like the Eternal has few advantages over the Vertex except that you only heat what you use for most part. Scaling issues worry me some though as once that heater has major issues a replacement is over $2K.

    Appreciate the input and will re read after dinner. All this helps so thanks to everyone who has posted!


    Quote Originally Posted by Dana View Post
    What the Vertex brings is 1/3 to 1/2 lower fuel use (depending on your total hot water volume use) than an atmospheric/power drafted 75 gallon unit, and a lower installed cost than a condensing tankess (with none of the quirks and fewer maintenance issues of a tankless. Depending on your water use & fuel costs (current and anticipated) the upcharge for a Vertex may or may not have a favorable net present value, but be sure to factor in any locale/state/federal subsidies you might get out of going with a condensing unit too. At even moderate volume hot water use a 95% condensing tank beats a 98% condensing tankless on fuel economy, since it never short-cycles. The only time the tankless beats it is on high volume use with mostly long draws. (The efficiency of any tankless on 0.5-2 gallon draws is pretty crummy.) From a "be nicer to the planet" point of view, lower fuel use is always better, of course, if the externalities beyond the IRR & NPV mean anything to you.

    The NEXT Hybrid won't cut it in this application, since it has only a 100KBTU/hr burner, and much lower storage volume than a 50 gallon tank- there's just no way to get to reasonable fill times on soaking tubs from here (you'd be better off with a 199KBTU/hr condensing tankless.) The biggest Eternal has a 195BTU/hr max, which comparable to a 199KBTU/hr condensing tankless, not better. It has fewer personality quirks, but the same maintenance issues of a tankless.

    What the Polaris brings is ~2x the anticipated lifecycle of a Vertex, primarily due to it's stainless steel construction. They are very comparable designs on the inside- you're paying for the stainless steel (which also has some scrap value after it's done.) Figure on getting at LEAST 20 years out of a Polaris, maybe even 30, compared to ~12-15 for the Vertex. The smallest-burner 50 gallon Polaris takes 130KBTU/hr-in, which is a significant up-sizing from a Vertex, which may effect fuel plumbing & regulator sizing, but it's enough to fill tubs that size.

    Both the Polaris & Vertex bring the potential for high-efficiency low-temp hydronic space heating to the table, if that's of any interest. Both are designed with ports already plumbed-in for combination hot water/space-heating applications, and it has way more burner than necessary for heating most houses, and is self-buffering- they can't short cycle on zone calls the way boilers can.

    Thermostatic mixing valves can go full-flow when the hot side input drops below the output setpoint- not all simple-minded tempering valves can, if you decide to bump up storage temps to 140F or beyond to get more capacity. (Basically, read the specs carefully when you buy.)

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    In the trades Dana's Avatar
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    If you want to get a better handle on whether the 76K Vertex would actually cut it, if we knew the gpm rating on the tub-filler/faucet the static pressure of your water, and the actual tub (not the sorta-like-almost) this is something that can be estimated fairly well. If the actual fill-rate at max-flow on your faucet would be on the order of 7-8 minutes (6-7 gpm at your actual water pressure) rather than 5 minutes (8-10gpm) you'll be just fine with the smaller burner. It's all about flow rates- at typical shower flow rates it would keep up literally forever. The 100K burner would keep up with ~3gpm forever.

    But since you don't need forever, it only needs to stay at 110F or higher at the output during the filling time. You have 50 gallons of buffer at the beginning, its a matter of how much heat it can put into the tank during the fill period, and what that does for the average temp of the water. A typical burner on a standard 50 gallon tank is putting less than half the heat rate of the smaller Vertex, and will deliver about 35 gallons at 10gpm before it starts running short on temp, which is more than enough for standard sized tubs. With a condensing 76K burner that extends to a bit over 40 gallons @ 10gpm, and considerably more at 7gpm.

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    DIY Junior Member Jdavis37's Avatar
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    Quote Originally Posted by Dana View Post
    If you want to get a better handle on whether the 76K Vertex would actually cut it, if we knew the gpm rating on the tub-filler/faucet the static pressure of your water, and the actual tub (not the sorta-like-almost) this is something that can be estimated fairly well. If the actual fill-rate at max-flow on your faucet would be on the order of 7-8 minutes (6-7 gpm at your actual water pressure) rather than 5 minutes (8-10gpm) you'll be just fine with the smaller burner. It's all about flow rates- at typical shower flow rates it would keep up literally forever. The 100K burner would keep up with ~3gpm forever.

    But since you don't need forever, it only needs to stay at 110F or higher at the output during the filling time. You have 50 gallons of buffer at the beginning, its a matter of how much heat it can put into the tank during the fill period, and what that does for the average temp of the water. A typical burner on a standard 50 gallon tank is putting less than half the heat rate of the smaller Vertex, and will deliver about 35 gallons at 10gpm before it starts running short on temp, which is more than enough for standard sized tubs. With a condensing 76K burner that extends to a bit over 40 gallons @ 10gpm, and considerably more at 7gpm.
    Thx Dana,

    With existing hardware (all of which will be replaced and thus another variable) I am getting about 5.25 gpm running 100% hot water. The error on this measurement is most likely on the high side. From your guestimates it would appear I have a decent safety margin assuming flow rate does not change drastically with new hardwar ein place or if for any reason line pressure changes and so on.

    I've looked at the Vertex prices for more guestimates and there is about a $400 difference between the 76K burner and the 100K burner. Compared to the total project budget this is not super significant and it would seem to make sense to just go with the 100K burner for adequate safety margin if needed.

    Flip side, the 75 gallon BW remains about half the price. Most likely these will be our 2 options. Just not sure I am "feeling" the eternal given am not sure it offers any real benefit over these 2 options with exception of the not heating hot water continuously part. I did look at the Eternal 195K unit specs and it seems 5 gpm is achievable with a substantial delta T so perhaps I should not be so quick to rule it out. In the end it may well come down to what the turn key price is given I most likely won't buy the water heaters on line, etc. Just too much risk of something going wrong and then having a big heavy object to "return".

    By the way we dont often run max hot water on multiple sources simultaneously and the highest water demand we have is filling the tub. Sounds like any of these options will work though again I would prefer to have some added margin to prevent not enough hot water disapointment!

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    In the trades Dana's Avatar
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    Be sure to do the math on any gas-piping upsizing you might incur going from a 76K burner to a 100K burner, too- if you need to bump up to 1-1/4" from 3/4" it will be a consequential number.

    It's hard to do the math with too many unknowns, the gpm at the tap actually matters when filling a 50 gallon tub with a 50 gallon tank. At 5gpm and a 130-140F storage temp you'd make it with the 100K Vertex. The average temp in the tank at the end of a 50 gallon draw would be about 75-80F, but it would be highly stratified, with 40F at the bottom by the dip-tube, but still hot enough at the top. The 100KBTU/hr 95% burner can make ~27 gallons of 110F water out of 40F water over the draw period, but you will have drawn about 40-45 gallons from the tank (the rest of the water in the tub being drawn from the 40F cold side of the mixer at the faucet &/or the cold side of the tempering valve.) With the mixing inside the tank due to the flow turbulence the top of the tank won't be the initial 130-140F, but it'll still be way over body temp, since the top 5 gallons of mix water from the first minute of flow would already be pretty much up to temp after 8-10 minutes of burner firing, even though the bottom 50 gallons would be downright cold. At (an unlikely) 15gpm it could be pretty marginal.

    The Eternal probably has a lower standby loss (it does have a mini-tank and at least some standby loss after all- it's not totally tankless) in comparison to a Vertex, but the standby loss of an atmospheric drafted 75 gallon unit is HUGE by comparison, due to convection through the center-bore heat exchanger. If you're using a whole lot of hot water on a daily basis the fraction of that standby loss isn't much, but if yours is a 2-person household that only fills that tub once/day at most, and pretty much sipping hot water the rest of the time, the standby loss can account for as much as 2/3 of the total fuel use.
    This type of standby loss doesn't happen with a Vertex (or the Eternal). Even though the "as-used" average thermal efficiency would never really be 95% for 50 gallon/day users, it'll still be above 60% even at 25 gallons/day average usage. But the 75 gallon atmospheric drafted tank would be netting under 40%, maybe even 30% under low-average load conditions.

    A PE named Robert Davis tested the earlier 90% thermal efficiency version of the 76K Vertex at various load profiles back in 2008- I have an archived copy of his data on one of my machines somewhere, but IIRC under high volume use it hit the low-80s, and at 25 gallon/day it was hovering just above 60%. This was compared to an atmospheric 40 gallon tank rated -EF 0.60 that hit the mid-60 under high volume use, and 40-ish at 25 gallons/day. There were 3-4 other models tested too, including a condensing tankless, that fared only marginally better on raw efficiency at any load profile than the 90% Vertex. A 75 gallon tank with a 75K burner has about twice the heat exchanger of a 40 gallon tank, and the convective losses will be proportionally higher too, even if the conducted losses through the sidewalls won't change as much. I can probably dig up one of the short-versions of the comparative reporting- PM me an email address if you want to see it.

    If gas stays ridiculously cheap the high standby loss of a 75 gallon tank may not matter, but if prices incrementally double over the next decade it might.

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    DIY Junior Member Jdavis37's Avatar
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    Quote Originally Posted by Dana View Post
    Be sure to do the math on any gas-piping upsizing you might incur going from a 76K burner to a 100K burner, too- if you need to bump up to 1-1/4" from 3/4" it will be a consequential number.

    It's hard to do the math with too many unknowns, the gpm at the tap actually matters when filling a 50 gallon tub with a 50 gallon tank. At 5gpm and a 130-140F storage temp you'd make it with the 100K Vertex. The average temp in the tank at the end of a 50 gallon draw would be about 75-80F, but it would be highly stratified, with 40F at the bottom by the dip-tube, but still hot enough at the top. The 100KBTU/hr 95% burner can make ~27 gallons of 110F water out of 40F water over the draw period, but you will have drawn about 40-45 gallons from the tank (the rest of the water in the tub being drawn from the 40F cold side of the mixer at the faucet &/or the cold side of the tempering valve.) With the mixing inside the tank due to the flow turbulence the top of the tank won't be the initial 130-140F, but it'll still be way over body temp, since the top 5 gallons of mix water from the first minute of flow would already be pretty much up to temp after 8-10 minutes of burner firing, even though the bottom 50 gallons would be downright cold. At (an unlikely) 15gpm it could be pretty marginal.

    The Eternal probably has a lower standby loss (it does have a mini-tank and at least some standby loss after all- it's not totally tankless) in comparison to a Vertex, but the standby loss of an atmospheric drafted 75 gallon unit is HUGE by comparison, due to convection through the center-bore heat exchanger. If you're using a whole lot of hot water on a daily basis the fraction of that standby loss isn't much, but if yours is a 2-person household that only fills that tub once/day at most, and pretty much sipping hot water the rest of the time, the standby loss can account for as much as 2/3 of the total fuel use.
    This type of standby loss doesn't happen with a Vertex (or the Eternal). Even though the "as-used" average thermal efficiency would never really be 95% for 50 gallon/day users, it'll still be above 60% even at 25 gallons/day average usage. But the 75 gallon atmospheric drafted tank would be netting under 40%, maybe even 30% under low-average load conditions.

    A PE named Robert Davis tested the earlier 90% thermal efficiency version of the 76K Vertex at various load profiles back in 2008- I have an archived copy of his data on one of my machines somewhere, but IIRC under high volume use it hit the low-80s, and at 25 gallon/day it was hovering just above 60%. This was compared to an atmospheric 40 gallon tank rated -EF 0.60 that hit the mid-60 under high volume use, and 40-ish at 25 gallons/day. There were 3-4 other models tested too, including a condensing tankless, that fared only marginally better on raw efficiency at any load profile than the 90% Vertex. A 75 gallon tank with a 75K burner has about twice the heat exchanger of a 40 gallon tank, and the convective losses will be proportionally higher too, even if the conducted losses through the sidewalls won't change as much. I can probably dig up one of the short-versions of the comparative reporting- PM me an email address if you want to see it.

    If gas stays ridiculously cheap the high standby loss of a 75 gallon tank may not matter, but if prices incrementally double over the next decade it might.
    I'm in contact with the guy who I will use to contract the bathroom remodels. Having this information will help me as I discuss things with both him and or his plumber if it goes that route. While I try hard to protect the environment, recycle religiously, yada yada yada, the bottom line on this one will first and foremost be having enough hot water to do the job and after that cost. The Vertex may well have a lot of strikes against it upfront most of them being cost (probably need new gas line, definitely need PVC piping cut through garage siding, and tank itself is $1K more than BW 75 gallon.

    Doesn't mean I won't use a Vertex though but do want to discuss with actual installer when time comes. Information here will be priceless at that point. Have learned a lot of "professionals" aren't all the same!

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    DIY Junior Member Jdavis37's Avatar
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    Follow up.... giving the Aquatic Serenity 4 air tub a hard look as it seems to offer what we are looking for at a decent price point. That said it has a capcity to overflow of 65 gallons.

    Based upon reading here a tub of that size would appear to be too big for the 75 gallon BW and I am guessing the Vertex may be strained. BW has some 100 gallon water heaters but am somewhat hesitant to go there. Lots of hot water being heated all day with such. May be the tub is going to cost money in long run and smaller tub would be called for.

    Assuming 5 gpm, what is the max volume one would feel comfortable for either the 75 gallon BW or 50 gallon vertex? Always can look bat at the Eternal Tankless given the size of the tub or even the 100 gallon BW but geesh that is a big water heater for a home! Thx

  15. #15
    Retired Defense Industry Engineer jadnashua's Avatar
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    You can get 75-80% of the hot water from a tank before it starts to cool off too much. Considering you will be mixing in some cold to fill the tub, you should get by with the 75G tank. If you might be needing additional HW at the same time, you need more, as you would if you couldn't wait for the thing to recover (IOW, if you needed to shower or wash dishes, you may have to wait a bit for it to recover after filling the tub). GPM only becomes an issue when you need to make hot water as you're using it...the tank preheated the full volume before you started, so you only have to worry about dilution from the cold, which is why the hot water comes out the top and cold is added at the bottom. Also, consider that that volume of the tub is without anyone in it, and you probably wouldn't fill it all the way to the overflow...it would tend to slosh around too much, so your actual practical fill volume would be lower.
    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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