>brand new< Bradford White gas water heater [mod: RG1PV50S6N] - not providing enough hot water. Why?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by johnny-canuck, Feb 4, 2020.

  1. johnny-canuck

    johnny-canuck Member

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    Location:
    Toronto, Ontario, Canada
    Apologies in advance for a veeeeerrrry looooooooooong post. But I'm stumped.

    Just before Christmas Day, I had a new rental water heater installed to service a WALK-IN tub that we had just added to our house about a month earlier.

    The new 50 U.S. Gal tank that was installed was a -> Bradford White model RG1PV50S6N = Gas, Power Vent, 50 U.S. Gal that has a spec'd "First Hour Rating (Gal.) = 78 U.S.Gal"

    Previously we had been using a similar ~7 year old rental RHEEM 40 U.S. Gal tank that had been servicing our entire house at least adequately for the previous 7 years (i.e. with a conventional 5' tub, 2 standalone showers, a clothes & dish washer, miscellaneous sinks etc.)

    When we replaced the conventional tub with the WALK-IN, we realized that the WALK-IN (for whatever reason … still to be determined (the reason for this post)) was basically unusable because the water temperature in the tub when it was full is not even close to 130F. As well, if you wanted to wash your hair at the end of the bath, you'd only be getting "cold" water from the tub's taps (much much less than the maybe even 100F you'd be reasonably expecting).

    So I made the simple decision that the 40 U.S. Gal tank was not cutting the mustard for the new WALK-IN tub (larger volume - nominally contractor told me it's capacity is 61 U.S. Gal (but obviously when a person is sitting in a WALK-IN tub they displace some of that volume, so it really uses less HOT water than when it's empty. (According to the web, an approximation for the volume a body would displace is ~10 U.S. Gal).

    So now I step back to try to figure out the cause of my "not enough hot water" problem and tell myself:

    1) the Bradford White 50 U.S. Gal tub has a "First Hour Rating (Gal.) = 78 U.S.Gal" … does that mean I can expect the tank to deliver ~78 U.S. Gal of HOT water (if it's thermostat is set at 130F) in it's 1st hour of use?

    2) when my wife is sitting in the WALK-IN tub, once it's full, she should only need around ~51 U.S. Gal of HOT water (61 tub's volume - 10 for a body) @ 130F (if that's what the tank is set to)


    … and after she's "soaked" she should still be able to wash her hair with at least reasonably HOT water (understanding that the tank's "recovery time" is also a consideration)

    So now I did a test.

    1. the WALK-IN tub is empty. I connect a hose from the TANK's drain valve and drop it into the WALK-IN tub and start filling the tub with ONLY HOT water directly from the TANK itself (no COLD is being mixed in).


    (I wanted to use a hose connection to take my HOUSE plumbing and the WALK-IN tub itself totally out of the picture).

    2. the tub starts to fill with HOT water at ~130F (I was using a Hot Tub floating thermometer, whose scale is set at 120F Max for safe Hot Tub use). It continues to fill the foot well area and starts to cover the seat area with HOT water. However once it reaches the seat level, you can feel the temperature coming out of the hose noticeably starting to drop. The tub continues to fill the area above the seat, the 1st 2 seat back jets and finally the top 2 seat back jets. The temperature of the water in the tub continues to drop as the colder water (coming directly from the drain valve on the HOT WATER tank) is mixing in and it drops from it's original 130F to less than 100F by the time it's full. Additionally, the temperature actually coming out of the hose itself, after the tub itself is full, is close to 70F and is not even close to being reasonably warm enough to wash your hair.

    My Question: Can anybody explain why this is happening? Is there something I don't understand about this kind of plumbing set up? Do I have a brand new Bradford White water tank that's a lemon / defective in some way?
     
  2. LLigetfa

    LLigetfa DIYer, not in the trades

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    Your test is flawed. By drawing from the bottom of the HWT with a garden hose, the cold water that enters the tank to replace what water you took out will go to the bottom since cold water is heavier than hot water. For an accurate test, you need to draw the water off the top of the HWT, not the bottom.

    You could get more hot water out by raising the temperature and installing a tempering valve to prevent scalding.
     
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  4. johnny-canuck

    johnny-canuck Member

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    Thanks very much LLigetfa !!! I'm at my wits end with this Walk-In tub problem. My wife is reasonably and definitely on my case about it. :)
    I can see now why my "test" is flawed.

    The contractor that originally installed the Walk-in tub had suggested it. But in fairness, he had previously suggested that I just crank up the thermostat on the tank, but I thought I was being smart and felt that I'd prefer not to fuss with anti-scalding protection on all my HOT water taps.

    Your response makes me think and ask ... can I install some kind of anti scald device at the water heater that would avoid replacing every tap in the house? Is that what you're talking about when you say a "tempering valve"?

    For now, I'm going to just try cranking up the temperature on the tank ... to its "Very Hot" setting (160F) and see what happens. (There's only 2 of us in the house and we'd be able to live with a "new norm" of having water that's much hotter than we've ever been used to, at all our HOT taps ... until I figure out a "safer" answer.

    Thanks again.
     
  5. LLigetfa

    LLigetfa DIYer, not in the trades

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    Yes, there are tempering valves that blend in a bit of cold water which can be installed at or near the HWT. Sometimes a separate line to the dishwasher is run before the tempering valve so that the dishwasher works better.

    Just remember to turn it down when you have guests. Perhaps you can find a setting below "Very Hot" that would be adequate?
     
  6. WorthFlorida

    WorthFlorida The wife is still training me.

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    A 50 gallon tank doesn't not mean 50 gallons at the set temperature. There was a post on this site a few months ago and he has a formula that when you draw hot water, cold water enters and the hot water temperature starts to cool down. There is a way to get the average.

    Besides, 130 degree water is way too hot. Check the installation manual, it will take only a few seconds to burn the skin. Do as LLigetfa suggests, install a tempering valve to cool the hot water down to about 120 degrees with the water heater set to 140 degrees. Also the big tubs absorb a lot of heat to even out the surface to the tub water temperature.
     
    Last edited: Feb 4, 2020
  7. dj2

    dj2 In the Trades

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    130 is way too hot for most humans, as WF said.
     
  8. johnny-canuck

    johnny-canuck Member

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    Location:
    Toronto, Ontario, Canada
    Thanks very much for all the responses. They've been very helpful.

    I plan to run a test fill of the tub this morning using ONLY the 160F water that's in the tank. I realize that this is (literally) an "overkill" kind of test but I'd just like to know what the water temperature would be finally be in the full tub ... and then I can plan to start dialing it down as I feel appropriate, to get to a safe solution using one or both of these possibilities:
    1. a water tempering valve
    2. simply dialing the temperature down on the tank ... but at the same time realizing that its "HOT" setting (120F) is not good enough
      • PS: thanks for the point about the dishwasher. I know they typically like to have water that's hotter than "safe" / 120F water. In fact I was wondering what 160F water would actually do to the stuff that we put in the dishwasher :eek:
    One last question for anyone.
    I started my search for a solution to my problem, based on the tank's specification of "First Hour Rating (Gal): 78". My thinking was that this meant the tank should be able to deliver (at least something close to) 78 Gal of HOT water (where HOT was whatever temperature the tank was set at).

    Since my new tank doesn't appear to giving me anything even close to 78 Gal of HOT water when it was set to its HOT (120F) setting in it's 1st hour of use … one of my thoughts was that I might have a lemon / defective tank, but I'm now thinking the tank's "Fist Hour Rating" isn't even close to what I thought it was telling someone.

    Can anyone point me at what they think is a good explanation of what the "First Hour Rating (Gal)" specification is actually trying to tell someone?
     
  9. WorthFlorida

    WorthFlorida The wife is still training me.

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    First hour rating gallon of water https://www.drftps.com/faq/what-is-first-hour-rating/

    It seems you are bent on needing enough hot water for the walk in tub which is understandable if a person needing to use daily. Installing a point of use tankless water heater maybe a better solution. The Chronomite site has dozen of models and sizes and some that you install on the hot water line to boost the heat output. Heat output is controlled by a microprocessor on some models and with an internal and covered temperature adjustment.

    Just last night I ordered one for my bathroom because it is less costly and easier than installed a recirculation system. We wait forever for hot water in the master bathroom sinks. I need to run new power and in my case it is easy to do. In your case you'll only be heating the water when needed, not in standby mode probably costing more. I ordered a CM15L/240 3880 watt unit and only $200+ from ZORO.com

    https://www.chronomite.com/home
     
  10. hj

    hj Moderator & Master Plumber Staff Member

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    IF you draw the "first hour rating" at a constant rate for an HOUR, you will get its first hour rating, however, during that hour, the water already drawn will be cooling down, so your container will NOT have the desired temperature in it.
     
  11. johnny-canuck

    johnny-canuck Member

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    Thanks very much. Definitely another possibility to throw into my bag of "solution" options. Sounds like it could be a reasonable possibility for my requirement ... and would be an alternative to investing in installing a "water tempering valve" to let me run the tank HOTTER than the standard "safe" recommendation / 120F.
     
  12. johnny-canuck

    johnny-canuck Member

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    Thank you. I just finished running my "overkill" test. The tank had been set to 160F and hadn't been used in the previous 2 hours, I filled the tub using ONLY the HOT water tap. It probably took about 15-20 minutes to fill it (less than 1 hour).

    The results (just as fyi for anyone that's considering Walk-In tubs and might see this thread later).

    At the beginning, the water from the HOT tap was off the scale of my Hot Tub thermometer (scale Max is 120F) ... presumably it was starting at 160F.
    By the time the water was a little over the seat area, I could feel that the water coming out of the HOT tap had cooled off significantly.
    The temperature in the tub at the very end when totally full was ~115F. So the final bathing temp, was obviously much less than 160F and I also believe the tub's volume is less than 78 US Gal.
    Also, the temperature of the water that was still coming out of the tap was now only COLD ... not usable to wash your hair.

    My conclusion? I don't think I got anything close to 78 Gal of 160F water from my tank. So I don't think my "test" results were close to the tank's spec'd value. I wasn't really expecting it to be. "specs" are just "specs" and real life is different.

    PS: I'll need to digest the link that WorthFlorida posted (https://www.drftps.com/faq/what-is-first-hour-rating/) to see if maybe it more closely reflects my "test results".

    Edit: I actually went to look at this site and it was easier to digest what it says than I thought.
    If your tank capacity is: 70% of your tank capacity is:
    30 gallons 21 gallons
    40 gallons 28 gallons
    50 gallons 35 gallons
    65 gallons 45.5 gallons
    75 gallons 52.5 gallons
    80 gallons 56 gallons
    100 gallons 70 gallons
    120 gallons 84 gallons

    In my case I have a 50 Gal tank, so this table is telling me I can only expect to get in the range of 35 Gal of HOT water. This makes sense to me because it's in the range of the volume of water I've put into the tub and I notice that the temperature has started to drop noticeably from the 160F that I was expecting.
     
    Last edited: Feb 5, 2020
  13. WorthFlorida

    WorthFlorida The wife is still training me.

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    Inlet cold water temperature impacts the results. Notice it is not a set temp, it’s temperature rise on rating plates. You stated it took 15-20 minutes. At three gallons a minute flow rate it is about 45 gallons.
     
  14. Estrogen Hostage

    Estrogen Hostage New Member

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    It’s possible that your dip tube on the inlet is broken, or the pipes are connected backwards. The inlet of the water heater should deliver water near the bottom, and when it’;s heated it rises to the top. The dip tube is a plastic tube about 1/2 the height of the water heater that delivers the incoming water to the bottom of the tank. If it’s missing, broken, or connected backwards then you will have a significantly reduced tank capacity.
     
  15. johnny-canuck

    johnny-canuck Member

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    Wow. That's a new possibility! Thanks.

    I'm just in the process of sending a note to a Manufacturer I've found, to get a recommendation on what size of "Electric + Tankless + Point of Use" water heater I could purchase and install that would be dedicated to servicing only the Walk-In tub. The Manufacturer I've located (Stiebel) has a Product Line (Eltron) of such water heaters and they sell in Canada, as well as the US.

    That said, is there any way for me to try to confirm the possibility you're describing myself? I'm sure the company that just installed my up-sized rental less than 2 months ago, isn't going to believe me if I have them come back to look at the brand new tank they just installed a 2nd time, but I'd like to try to at least rule it out, if I can. ("Lemons" aren't common, but they do exist).
     
  16. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    One thing to also look at is the tub fill valve. Many, not all, if it doesn't contain the ability to run a shower, will have an internal maximum temperature stop. This can limit how hot the actual output will be as it could always be mixing in some cold at the fill valve.

    Most modern tub/shower valves have a way to adjust the hot/cold mix to limit how hot it can be. A true thermostatically controlled tub valve usually only has an adjustment to calibrate the thermostatically controlled valve so the temperature is what is indicated on the dial.

    Large tubs, or showers with multiple shower heads will require a much larger WH than most people would consider. As was noted, you can never get the full volume of the WH out at the desired temperature...it will stay fairly constant until near the end as the incoming water cools off what's left. That's why they fill from the bottom and draw off of the top...the heated water is lighter, and tends to stay near the top, but eventually, the incoming water will reduce the temperature.

    The larger your draw volume over time, the less likely the first hour rating will make much sense. IT tends to work out for say a shower where the gpm is fairly low, but not when it's gushing out at high volume. A good tub filler could reach in excess of 14gpm, so if you can use say 35 g out of the 50 in the tank, that's barely 3 minutes. A typical 1/2" valve draws maybe a max of 5-6gpm, depending on your temperature setting, so maybe six minutes or so. Keep in mind also that the Copper INstitute's recommendation for maximum water velocity on hot water is only 4gpm on hot water in a 1/2" pipe. IT doubles to 8gpm on a 3/4" pipe. Their spec is at 5fps maximum, and the gpm numbers are calculated from that and the ID of the pipe involved.

    There are WH that have larger burners, that can produce lots more hot water in a short time.

    At 78gph, you could draw water at barely 1.5gpm and maintain the outlet temp. Drawing more
     
    Last edited: Feb 8, 2020
  17. johnny-canuck

    johnny-canuck Member

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    Thanks for the response. I believe I understand the point you're making about "pressure balancing" and/or "thermostatically controlled" faucets. I'm almost positive that I have a very basic MOEN 2 handle faucet with a shower diverter (it just diverts to a hand held shower). So I'm pretty sure there's nothing at the actual faucet that might be part of the problem. It's a 1 piece unit with a filler spout + 2 handles + shower diverter knob you pull, that sits on the top deck edge of the tub (photo is attached).

    Also, your expansion on how to interpret the "first hour rating", also appears to be in sync / explain the problem I'm seeing.
     

    Attached Files:

  18. johnny-canuck

    johnny-canuck Member

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    Hi WorthFlorida,
    I followed up on your suggestion of getting a {point of use - electric-tankless} type of water heater for my Walk-In tub problem (not enough hot water from our 50 US gal tank). I found a company (STIEBEL -> models of their ELTRON line) that sells things like this in both the US and Canada, so I asked them for a recommendation

    They understood my basic situation (wanting to have enough hot water for my Walk-In tub) and gave me 2 options. For me, both of the options are not practical. I have a "century" old house with only 100 Amp service, so the cost of simply installing the electrical requirement is prohibitive for my requirement. Presumably their product line is designed for new construction and more demanding requirements.

    I'll have to take a closer look at the CHRONOMITE line you've suggested. For what it's worth ( / other members that might trip across this thread), I'm posting the response I got from STIEBEL re their "Eltron Tempra 20 Plus or 24 Plus" models.

    ================
    I have been going back and forth with the senior tech over at Stiebel to get a better idea of our options for you. Unfortunately it really comes down to only one solution that would work best.

    What they recommend is using a Tempra 20 Plus or Tempra 24 Plus unit plumbed on the hot water line just before the tub. You can input up to 131° water into the Tempra, so once the tank is depleted the Tempra would kick in and finish filling the tub. The downside is that the flow rate these units can handle would be fairly low - about 2.0 - 2.5 GPM (this is of course once the hot water tank is empty and the water passing through the unit is around 40-45F.

    The plus side to this would be that your wife would not need to wait for the tank to reheat in order to use the handheld shower as the Tempra unit could provide ample flow for that use.

    These units do require a fair amount of electricity so that is another thing to consider.
    The Tempra 20 Plus : 2 x 40 AMP double pole breakers, #8 wire, recommended 150 amp service. $839.00
    The Tempra 24 Plus : 2 x 50 AMP double pole breakers, #8 wire, recommended 200 amp service. $872.50

    Let me know if I can answer any further questions for you.
    ================
     
  19. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Generally, unless attached to a large tank, heating water with electricity, especially on demand, requires LOTS of current.

    If you have room for it, there are some electric tanks that can be run off of lower current. Their recovery rate will be slow, but unless there is a need for extended, long-term use of hot water, could you add a second tank, maybe in a closet? Electrical WH don't need the same space as say a NG or propane tank.

    There are other NG WH with larger burners and a larger tank. IN a heavy draw where there's not much time for the burner to recover, keep in mind that you usually can't get much more than about 70% of the tank's capacity out before things start to cool off.

    You can make the tank appear to be larger if you raise the storage temperature. To stay within code and for safety reasons, you should add a tempering valve to limit how hot the water will be coming out of it. But, by mixing that hotter water with some cold, you'd be storing more energy, and thus, get more volume of hot water at your tub or shower.
     
    Last edited: Feb 14, 2020
  20. johnny-canuck

    johnny-canuck Member

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    Thanks for the input. I'm just beginning to get a bit of a sense of sizing electric "tankless - point of use" type solutions ... and understanding the "heating capacity" and flow characteristics you get with different "models" (increased power load (wattage) that I'd need to make available in my house + how quickly I might be able to expect to feel the benefit at my target plumbing fixture (water flow rates etc.).

    It's turning out to be far more involved than I had thought. Now that I understand more, I'm leaning toward simply cranking the temp on our gas tank's thermostat and installing a "water tempering" device to the top of our existing tank. It's the next thing I'll need to learn about :)
     
  21. WorthFlorida

    WorthFlorida The wife is still training me.

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    What I liked about the CHRONOMITE brand is the size and they had nice charts on water temp rise vs per gallon flow rate for each model per voltage and wattage sizing. Also it is microprocessor controlled to keep the output temp steady, from 105-120 degrees based on the setting. I saw one unit in a public bathroom so the model I picked fits under the cabinet with no problems. They do have larger units for shower and bathtub fills.
     

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