Tankless water heat lag to closest faucet

Discussion in 'Tankless Water Heater Forum' started by Kevin Wang, Jan 4, 2014.

  1. Kevin Wang

    Kevin Wang New Member

    Messages:
    1
    Location:
    Texas
    I just bought a brand new home with a tankless water heater. My problem: it takes minutes to receive warm water to my kitchen sink which is the closest faucet to my garage-tankless heater. The water never reaches the hotness of my shower upstairs, which receives hot water within a minute. Seller adjusted the hot/cold valves under the kitchen sink but it still takes forever to reach warm temperature. Sometimes, it never gets warm.

    I have not washed hands in warm water in any bathroom faucets either (don't have it on longer than 30 seconds to see if it ever warms up).

    I'm not sure if this is what I should expect with a tankless water heater, or if I need to complain to my homebuilder given I have a 1-year warranty on everything. Any tips by you experts out there on how to troubleshoot this further to determine if there is a defect in my plumbing or if this is working "as intended"? Should I feel the pipes coming out of my water heater and time how long before it gets hot? Thanks for any help.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,822
    Location:
    New England
    Whenever the WH is located a long ways from the point of use, it takes time to purge the lines of the room temperature water there, unless it was run recently and some is still warm. The alternative is to recirculate the water like is done in large buildings. But, with many tankless systems, it can either void or significantly shorten the warranty on the unit.

    The tankless systems also have a minimum flow before they'll turn on, so it may never be enough if you have the faucet set to what normally would have been warm. Once they turn on, they may stay on until the flow stops, but getting an initial warm may be tougher.

    There are a few recent threads on similar issues...check this forum and read a few.

    But, once you do get hot somewhere, it should be about the same temp.

    The only other thing I can think of, and it normally isn't an issue with new faucets, is if one of them is defective, and is effectively creating a cross-over - this would dilute the hot, potentially considerably. Do you have anything like, say on the washing machine that connects cold with the hot? Try shutting the valves to the washing machine off and see if it makes any difference. It shouldn't, but it won't hurt to try.

    It may help to also know the brand and model of the tankless unit.
  3. Smooky

    Smooky Member

    Messages:
    569
    Location:
    NC
    There may be a mixing valve/tempering valve that needs to be adjusted. If the faucet aerator is clogged it takes longer to purge the cold water out of the pipes. Maybe a different type of aerator would help. I think I would open both valves under the sink, all the way.
  4. Terry

    Terry Administrator Staff Member

    Messages:
    14,798
    Location:
    Bothell, Washington
    Most tankless water heaters come preset for 120 degrees.
    In the shower, that seems like plenty of heat. Washing hands or doing dishes, that feels colder.
    An easy fix may be to reset the tankless up to 140. I have used them both ways, one home at 120 and the other at 140.
    Regardless, it does take more time to get heated water with tankless unless you have a recirc line to keep the line warm to the faucet.
  5. TheLex

    TheLex New Member

    Terry, but from what I've read once you hook up a recirc line, the warranty on the typical tankless heat exchanger drops from 15 to 3 yrs. That's quite a dramatic drop in warranty period. Is that something to be concerned about? Do the manufacturers know that with a recirc line the heat exchanger is going to fail sooner?
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,822
    Location:
    New England
    The unit will fire more often. You sometimes also see that sort of warranty change when something is used in a commercial situation verses a residential one.

    Tankless systems, at least most of them, are not designed for continuous operation like a boiler used for heating. With a recirculation system, they would run much more frequently, and that can take a toll.
  7. TheLex

    TheLex New Member


    Oh I understand that. But the manufacturer will also state that HEATED recirculated water also shortens the warranty. IOW, if I run a separate electric heater to maintain a reserve tank and that tanked water gets recirculated to eliminate the cold water sandwich effect, the manufacturer also shortens the warranty for that application. This despite the fact that it's the small electric heater that is maintaining the recirculated water temp, not the main boiler on the the big tankless unit.
  8. Soapm

    Soapm New Member

    Messages:
    50
    Location:
    Aurora, CO
    Did you follow the pipes to see if it's piped as the closest or does the piping take some strange route?

    What kind of facet is this? Is it a one knob job? Never reaching complete "hot" temp sounds like it's mixing with cold. I wonder if you're not getting full hot water and it's constantly mixing predominately cold. I don't know how the pro's would check but I would take the hot line off below the sink and see if you get the same results there shooting the water into a bucket or via a short hose into the drain.
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