Tankless water heater takes forever to supply hot water at faucets

Discussion in 'Tankless Water Heater Forum' started by surfix007, Jan 1, 2014.

  1. surfix007

    surfix007 New Member

    Messages:
    3
    Location:
    Princeton, NJ
    First of all a 'Happy New Year' to everyone!
    I am new to this forum and as far as I can see, not the only one with this problem. However, some of the postings that almost perfectly fit my scenario are almost 2 years old and perhaps technology has some more options available to solve my problem. Although coming from (cold) Germany where all water lines are insulated by law, our contractor felt that this was not necessary over here in the Mid New Jersey area ;-( (should have done it anyway)...
    Here is our problem: It takes at least a minute or more for the water to get warm and even more to become hot. The amount of water wasted is just terrible. Here is our setup:
    We have a Navien NR240 tankless heater in the basement. The heater has no internal buffer (the contractor bought the cheaper model). The bathrooms are on the 2nd floor. We have almost everywhere pedestal sinks and a bathtub/jaccuzi in the master bathroom.
    I thought about several options but I am not sure what would be best and would appreciate to get some feedback:

    Option 1: External buffer tank.
    Because the Navien does not have an internal buffer tank, a small external one could help to have hot water available (at least at certain times) and we would only waste the water in the pipes? I looked around but have not really found anything and putting a 40 gallon tank there would probably defeat the purpose of a tankless heater ..

    Option 2: Circulation pump (e.g. Grundfos UP15-18SUF)
    This looks like an interesting option because the e.g. Grundfos pump runs with a timer and we only would need it a couple hours during the day. I guess, the UP15-18SUF should be fine it has around 11 feet of head range which should be enough from the basement to the 2nd floor (am I right here???).
    Further more, the installation seems to be minimal - no need to rip open walls etc.

    Option 3: Hot water delivery system (e.g. CP600 or similar)
    This also sounds like a feasible solution. I like that this solution because it only runs when needed, however, the problem is that I don't really have space under the sinks to install a unit. The only place this would work is to put this in the enclosure of the jaccuzzi which is not too far from shower and sinks, but I am not sure if this would still work. How would it sense the hot water if it is installed in a different branch of the pipe???

    Anybody knows of some better ideas, other options or how to optimize one of the listed options?
    Thank you so much for your help!
    And once again, all the best for the new year!
    Regards
    Rainer
    Last edited: Jan 1, 2014
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,334
    Location:
    New England
    WRT a circulation pump, in a pressurized, closed system, the head pressure isn't much of an issue...the water falling back down helps pull the water up from the WH. The pump only needs to overcome friction and open the checkvalve. Read the spec sheet carefully on the tankless system, it may not allow a recirculation pump (voids the warranty), or if it does, may require other items as well.

    Rather than use a timer, some of them can be fitted with a momentary activation circuit...in this, when you want hot water, you press a button, and the recirculation system runs until you have hot. At least you wouldn't be dumping water down the drain, but you would have to wait the same amount of time for the pump to bring hot to the tap.

    Your problem is not unique to a tankless system...you'd have the same issue with a tank. The tankless may be slightly longer, since it does have some ramp-up time to actually generate some hot verses a tank where you are only flushing the lines with already hot water.

    Having lived with tankless systems in both Europe and in the USA, I must say that I still prefer a tank, especially if you have a boiler to heat it. Tankless does work well when it can be close to the point of use, and is sized adequately for the local incoming water temp and the anticipated max use.
  3. breplum

    breplum Member

    Messages:
    63
    Location:
    San Francisco Bay Area
    Call back the idot plumber

    First, you should request that the plumbing contractor take back what they sold you and put in the more suitable and modern NPE series model. Frankly, it was an unforgivable blunder using the NR series.

    There is on the market, Grundfos "Comfort System". It might be your best bet.
    It is a "one pipe" recirculation system.
    It utilizes a crossover at the farthest fixture, but the pump can be mounted near the water heater, so power is not an issue under the farthest sink.
    You didn't say where the WH is located, but the Grundfos solution is not listed for exposure outdoors.
    The big downside to the Grundfos Comfort System crossover mixing, is that you end up with hot water mixed with cold at that farthest outlet, but that's what you get when there was no dedicated recirc. pipe installed.

    Frankly, it is unforgivable that your plumber did not at least get the NPE series Navien water heater with BUILT IN buffer tank, check valve and recirculation pump.
  4. Soapm

    Soapm New Member

    Messages:
    50
    Location:
    Aurora, CO
    My $00.02... I would live with the one minute delay since most of the recirculation methods void the cost savings of going tank-less. If you're going to continually heat water then it's cheaper to get a tank. The push button or set ups like in this thread still allow the cost savings of being tankless but still make you wait the minute for the hot water.

    In my experience, being tankless changes the way you do things but eventually the new way becomes habit. I wash my hands with cold water, turn on the water before grabbing the toothbrush and toothpaste, and you have to teach yourself to turn on the shower BEFORE you turn off the sink or you'll get a cold water sandwich sure as can be. I turn on the hot water while I load my whites in the washing machine so when I turn on the machine the water is hot. Same with the dishwasher. And our tankless is set to 125 so the whites and dishes are cleaner.

    I built a recirc system like the one I linked at the do it yourself where you could turn a faucet on then off to start the loop heating but in time I realized I didn't need it. I know it takes time to get hot water so I've arranged my sequence of doing things to work with what I have instead of wishing I had something different and the only difference I notice now is my shower doesn't get cold if I go after my daughter or wife.

    Now there is a downside to tankless, a tank water heater times your showers for you. After about 15 or 20 minutes you begin running out of hot water so you know to rinse and get out. The tankless doesn't have that feature so now my wife and daughter take 45 minute showers and insist there is no way to be sufficiently clean in any less time. I wish I could put a 20 minute timer on my tankless...

    ps... The best way to reduce the wait time is install the heater close to the point of use. Most installers put the heater close to the gas entrance. I bet if you look around you will see there was a much more logical place, closer to the point of use to put the tankless. My installer said the gas line could only be xxx feet from the meter or we'd have to get a larger line except he placed ours xxx feet in the opposite direction from where the water is used. Now I did take pex and ran our delivery line more direct which took about 15 seconds off our wait so now our delay is more like 30 seconds which is close to what it was when we had a tank.

    Good luck and good new years to you and yours...
  5. surfix007

    surfix007 New Member

    Messages:
    3
    Location:
    Princeton, NJ
    Thank you for your answers!
    I will continue to search through the threads - there is really a lot out there. I need to find something that will pass the WAF factor ;-)

    @jadnashua: I checked with the Navien manual. It only says that the external pump needs to be able to do 2+ GPM and that a check valve is installed (I guess I would put in an antigravity valve which would do the same - right?). I also saw some very interesting comments from you in other threads - thanks!

    @breplum: Yes, I had a couple of fights with the contractor and the plumber. Although, the contractor did a beautiful job with the framing etc., he hated everything that was newer then the 60s. I am not sure how long you can call back the plumber. It's our 2nd winter season. In the first winter we thought it has to do with adjustments etc. During the summer, this isn't an issue and this winter it's really bothering us. How long would he be responsible for? Also, do you know how to size the Grundfos? I was looking at 2 models: the UP15-10SU and the UP15-18SU ...

    @Soapm: I definitely would not run the pump 24/7. Primarily during the morning and evening hours and if absolutely needed add a second device (with a button) at the kitchen sink. This way the energy usage would not increase too much but we wouldn't need to run the water for minutes ...
    Regarding your wife and daughter, there is an easy solution: just turn on a different hot water faucet (between the heater and the shower) and they will experience a cycle of hot and cold - very annoying ;-) The link you posted does not work - could you please post it again?

    In general: I guess one of the biggest challenges is the WAF. My wife hates remotes and when I tell her to take her smartphone to the bathroom in order to get water - oh boy! Therefore, I am more thinking of a timer that would turn the pump on at specific hours during the day.
    Does anybody have any experience with Watts? I could get them at the local home depot. So far the reviews seem to be ok and they are about $50 cheaper then the Grundfos. Any idea?
    Thanks
    Rainer
  6. Terry

    Terry Administrator Staff Member

    Messages:
    15,423
    Location:
    Bothell, Washington
    If a recirc was wanted, that could still be added to this water heater. Or the NPE could have been used.
    You don't buy the lower priced unit, try it out a few months and then decide that you should have bought a more expensive unit using more piping. You learn from it.

    If you install the recirc, I like to use an aqua stat that turns off the pump when the return line has warmed up. That prevents constant pumping. The Grundfoss Aquastat runs $30.00
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,334
    Location:
    New England
    I have a Redy-Temp recirculation system...self-contained, install under the furthest point of use (typically someplace like the vanity in the bathroom), installs in literally minutes, but has a fairly big if...you have to plug it in. WHen I did my remodel, I installed a receptacle in the vanity for it - dropping down from the existing one off the load side of the GFCI was easy. It has a built-in pump, crossover, check valve, and adjustable aquastat. I have it set so that the water at the vanity is just warm (the shower is closer, so gets hot almost immediately). I also have it on a timer. If your water pipes are insulated (most of mine are), I find that mine runs about a minute, 4-5x per hour. I'm sure this cycling will shorten the life of the pump verses one running constantly, but it's been there now almost 10-years and still works and sounds nice and quiet. It is not one of the cheaper units out there, but it does work...you pay for the convenience. Not that I couldn't pipe in a more typical one, but I live in a condo, and would have had to pay someone with a license to do it...this is installed by taking the hoses off the supply lines, reattaching them to the unit, and then running a new set back to the supply shutoffs...then, you plug it in, adjust the knob for the temp for it to shut off and walk away. Well, if you use a timer, you have to program that silly thing, but that has nothing to do with making it work in the first place.
  8. surfix007

    surfix007 New Member

    Messages:
    3
    Location:
    Princeton, NJ
    Once again, thank you for the suggestions. I included a drawing (very basic) that shows the current setup. I guess one idea would be to add a "Redy-Temp recirculation system" inside the enclosure of the jacuzzi. The benefits would be that it would not be necessary to touch the piping at the heater (if I understand this right - jadnashua???) because the unit would be installed at the faucets of the Jacuzzi. there is enough space and electricity available. Although, this faucet is not used daily, the pedestal sinks as well as the shower would benefit from this.

    However, one more question: The hot water line splits right at the ceiling in the basement. The master bathroom is on one end (the longer one) and the kids bath at the other end. With a Grundfos pump or similar I would just add a 2nd control valve (one in the master bath, one in the kids bath). However, how would this be done using the Redy-Temp solution?

    2014-01-02_14h44_38.png

    @Terry: Great forum! When I understand correctly, you mean that I can still add the buffer tank and recirc to the Navien??? I checked but couldn't find anything. Would you know where to look for this kit? I agree about the more expansive unit, however, at the time being we didn't know enough about it and did rely on the recommendation of the plumber ;-(

    Thanks
    Rainer
    Last edited: Jan 2, 2014
  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,334
    Location:
    New England
    With the pedestal sinks, there'd be no place to hide the Redy-Temp system I have...but they do make other versions. The version I have works well when you have a vanity to hide it and are willing and capable of getting it power.

    If you can't plumb in a dedicated return line, you must have a crossover, which might be hard to hide at the sinks. You may have room underneath the Jacuzzi, so the shower, being closer would get hot much sooner as well. The sinks, a smaller wait than now, but not as good as if you could put a crossover there. The crossovers vary in size, so you may still be able to put one in at the sinks, but it may just be easier at the tub.
  10. TheLex

    TheLex New Member

    I may be wrong on this point, but from what I've seen, the tankless heater manufacturers downgrade the typical 15 yr warranty on the heat exchanger to 3 years if you run a recirculation line. Just thought I'd mention it. It may not matter to you.
  11. MikeQ

    MikeQ New Member

    Messages:
    87
    Location:
    Washington
    That is on gas fired heaters?

    Stiebel Eltron only makes electric on demand heaters but they do not downgrade the warranty when used with a recirculation line. They actually provide a handy diagram showing a proper recirculation install:

    http://www.stiebel-eltron-usa.com/pdf/tsb_tempra_recirculation.pdf

    One of the benefits of electric on-demand (over gas fired on-demand or tank style water heaters) is the versatility of mounting location (no flue required). This can allow placement very close to the point of use and reduce wait for hot water to a minimum. That was one of the main reasons I ditched my tank style heater. I really appreciate how fast the hot water arrives.

    American homes are often plumbed with over-sized supply lines that travel excessive distance to the point of use. This is a huge problem with any type of heater. Some people think we need a gazzilion gallons per minute of hot water capacity. I'm happy with a steady flow and with an on-demand water heater that steady flow is dependable - it never runs out like it does with a tank style heater. I plumbed my hot supply lines with 1/2" pex using the most direct route feasible instead of using 3/4" trunk lines and 1/2" feeders taking a more roundabout route. The result is hot water fast.

    I am not a fan of hot water recirculation loops due to wasted energy, unnecessary pumps, etc. It's even worse in the summer when such lines are heating the interior of your home beyond comfort levels, especially if the air conditioner needs to run more to get rid of the wasted heat. Terribly inefficient.
  12. so what are you complaining about???


    long delays in getting hot water is normal
    that is the nature of a tankless water heater...
    so why do you complain??

    you must be willing to get used to the delays and the
    sandwhiches in hot and cold water you will receive with
    a tankless water heater.....

    you must modify your life-style
    to better enjoy and understand the tankless experience.....
    tankless is a green mind set, because you think you are doing
    something ecological and good for the planet.... ...


    I tore out a 5 year old bosch last month and installed a 40 gal
    rheem heater,,,, the older couple were very, very happy with the new heater.
    because they were tired of not being able to run 2 appliances
    at the same time.......

    I will be getting back with them in a short while to
    see if they notice a huge increase in their gas bill,
    perhaps maybe 8 bucks a month

    I hung their bosch on my showroom wall next to a couple other
    brands I have collected over the years....



  13. TheLex

    TheLex New Member

    So what are you saying? That if I got with two 100k btu Vertex 100's or a couple of Bradford White 75 gal 76k btu tank units, that I'd have $16 more in gas bills a month than a couple of 199k btu Tankless water heaters? But then I'd have no cold water sandwich and I'd save about $6k? Hmmmmmmmmmmmmmmmm.

    What to do. What to do.


  14. MikeQ

    MikeQ New Member

    Messages:
    87
    Location:
    Washington
    That is not my experience with tankless heaters. I've never used a gas fired tankless (that I was aware of anyway) but the electric heats very quickly, the delay is primarily flushing the lines between the heater and point of use. This problem is not unique to tankless - all water heaters have this issue and the further the heater from the point of use, the worse the problem.

    Again, not my experience. Once it gets hot (and it doesn't take but a few seconds) - it stays hot.

    No modifications have been necessary. In fact, the endless water from a tankless system is actually much more convenient. Here's one example:

    Over the holidays I had 8 people for 8 days. There was no need to stagger showers or laundry throughout the day because the endless supply of hot water never got cold (even with two showers running simultaneously and back to back showers). With a tank style heater My guests would have to modify their lifestyle to avoid showers turning cold. I would have to plan to do the laundry around busy shower times. The endless hot water meant I didn't have to ask my guests to take short showers either.

    I switched not for environmental reasons but for the luxury and convenience of endless hot water and also to free up the wasted storage space taken by the hot water tank.

    I run three appliances simultaneously with my electric on demand. Bosch units are very cheaply constructed - I would avoid them in favor of a unit with a 100% copper heat exchanger and automatic flow regulator like the Steibel Eltron Plus series.

    BTW, posting in a larger than standard font does not help you make your point.
    Last edited: Jan 16, 2014
  15. Nik4Me

    Nik4Me New Member

    Messages:
    3
    Location:
    RI
    Steibel Eltron

    "I switched not for environmental reasons but for the luxury and convenience of endless hot water and also to free up the wasted storage space taken by the hot water tank.



    I run three appliances simultaneously with my electric on demand. Bosch units are very cheaply constructed - I would avoid them in favor of a unit with a 100% copper heat exchanger and automatic flow regulator like the Steibel Eltron Plus series. "


    Mike, I am thinking of ditching my 40 gal gas fired tank in favor of electric tank-less this month
    I know, that I am going against all economic reasons and against a gas trend crowd with a lot of economical and reliable products available.
    My reasons are house air volume exhaust related as well as health related (natural gas burn produces a lot of undesired chemicals and a lot of moisture, which I do not need- I am running a whole house dehumidifier now nearly non-stop) Money is an issue. I zeroed in on Steibel, so I am glad to see you mentioned it.
    Can you please tell me what model do you use/recommend? I may not need as large as yours- small family, 2 full baths. Usually we use the shower in one bathroom upstairs. If you know it, is it possible for you to share how many Kw per month do you attribute to your tank-less use ?
    That will help me with budgeting and preparing my significant other for expected increase in monthly electrical bill
    Thank you
  16. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,334
    Location:
    New England
    There are some gas WH that are closed combustion - i.e., they get their combustion air from outside in a dedicated pipe (sometimes concentric with the exhaust). In this manner, it would have absolutely NO impact on the house's air quality or affect infiltration rates. Gas, when available, is MUCH less expensive to heat water than electric in almost every market.
  17. MikeQ

    MikeQ New Member

    Messages:
    87
    Location:
    Washington
    I'm not an expert on gas appliances but, I was under the impression that a properly vented modern gas water heater does not add any moisture to the living area. If you have gas available I would strongly recommend you explore gas options (tank or tankless) that preserve your air quality. A gas range is not vented so it will affect indoor air quality but a vented water heater should not be an issue except for the make-up air which can be solved as Jim has already mentioned. You will also save money.

    I went electric only because it was that or propane which is much more expensive than natural gas.
    Last edited: Apr 7, 2014
  18. Dana

    Dana In the trades

    Messages:
    3,029
    Location:
    01609
    MikeQ is dead-on the money- if a gas hot water heater is vented in a legal matter it won't raise the humidity levels in the house.

    Having to run a whole house dehumdifier in an RI location means you either have huge ground moisture drives, huge air infiltration issues (in summer, anyway) or inadequate exhaust ventilation for bathroom & cooking or some combination of the above. It's kinda important to figure out which, and which can be most-easily remediated. (If it's air infiltration there's pretty big payoff in comfort and heating/cooling bills by fixing the leaks.)

    An electric heat pump water heater would help dehumidify the house (it puts the heat of vaporization of the condensed moisture into the hot water tank) and takes less instantaneous and annual power to use then any electric tankless. They're a bit noisy, but it's probably a better choice here than a tankless when you factor in all the issues.
  19. Nik4Me

    Nik4Me New Member

    Messages:
    3
    Location:
    RI
    Thank you everyone for great suggestions: implemented some of them already. Moisture comes from a windy ocean side: have to open doors to enter the house and windows to air the house from time to time. Thinking of moving to New Mexico!!
    Ground water table is high as well, spot on- water vapors through concrete basement- that is were the dehumidifier is located. Found SaniTred product, but unable to prep the surface according to their requirements and concerned that some off-gassing will make things worse.
    Well sized ventilation systems in kitchen/baths are present and used.
    Another concern is natural gas health effects: have to read between the lines and follow links for more information as this is coming not from the treehuggers, but from our government who is there for big business:
    http://toxtown.nlm.nih.gov/text_version/chemicals.php?id=18

    I think it is the Russians who say -if you don't drink and smoke- you die healthy! Nevertheless, a lot of health issues in the family- air related.
    Thank you everyone for great responses- will keep studying the issue.
  20. MikeQ

    MikeQ New Member

    Messages:
    87
    Location:
    Washington
    The health risks noted in the link you provided are from breathing the raw natural gas or the combustion by-products. A properly installed gas water heater will not leak raw gas or the combustion by-products into the living area.
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