Tankless & Single Handle Facuet?

Discussion in 'Tankless Water Heater Forum' started by jgcalifornia, Nov 19, 2013.

  1. jgcalifornia

    jgcalifornia New Member

    Nov 19, 2013
    los angeles CA 91607
    We were interested in the Marey 10L NG DP tankless water heater. After reading several reviews on this model, as well as other manufacturers, it seems none of these work with a single handle faucet.
    Seems strange that you would not be able to use a single handle faucet with these heaters..as most kitchens have this style..
    Does this rule apply to all tankless water heaters?

    Marey said: The reason being, that all of our units are pressure activated. When you lift your handle up and to the hot side, the pressure will activate the unit. When you start to move the handle to the cold, you are diverting the pressure from the hot, to the cold, so the unit will deactivate. When you have dual faucets and are adding in the cold, you are lessening the pressure as well, but not completely diverting it."

    Thanks for any help or info.

    Last edited by a moderator: Nov 19, 2013
  2. guy48065

    guy48065 Member

    Sep 26, 2013
    SE and north MI
    Activation flow rate can be an issue with many tankless heaters but ordinarily you're only interested in constant warm flow while taking a shower--and shower valves usually flow enough to keep the heater active. Pretty much everything else you can run hot, then cold...or "suffer" a bit washing your hands in cold water.
    Or remove the restrictor.
    Depending on the heater's distance from the faucet there may be enough hot water in the pipe to wash--even if the heater turns off.
    Last edited: Nov 19, 2013
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  4. Reach4

    Reach4 Well-Known Member

    Sep 25, 2013
    Just looking at literature, the RTG-84 models http://rheemtanklessonline.com/models.html will accommodate .26 GPM Minimum Flow Rate, .40 GPM Minimum Activation Flow Rate. Those would seem to be workable with single control fixtures.
  5. jgcalifornia

    jgcalifornia New Member

    Nov 19, 2013
    los angeles CA 91607
    So unless I buy the bigger model, which has a computer chip, it wont work...Just seems strange that you wouldn't be able to use this type of faucet for a smaller tank.
  6. Dana

    Dana In the trades

    Jan 14, 2009
    Marey is the absolute bottom-of-the-barrel minimalist tankless available in the US, as reflected in the price. (Their limited safety agency certifications aren't sufficient to be legally installable everywhere in the US either- in MA an already-installed Marey would be condemned by the code inspector. YMMV.) There are other relatively cheap dumb as a box o' rocks tankless units from Bosch, Paloma etc that also have mechanical pressure feedback that can still work fine with standard tap mixers at ~0.8 gpm, though none of those really control temp well at low flow.

    If it's already installed you might get the Marey to work if you set the output temp control on the unit itself as low as possible so that it's delivering 110F water at most, and don't try to just dribble the water out of the tap, give it a good amount of flow. There's no point to setting the output temp of a tankless any higher than you'd want to see at the taps, since (unlike tank heaters there) is no volume of water stagnating at Legionella temperatures, and 100% of the water in the water heater is purged with every hot water draw. Showers are typically ~105F, tub bath fills ~110F. Some people just set their higher-tech tankless units to 106F and forget it- it's good enough for most purposes.
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    Lav faucets are flow restricted, showerheads are too, but at a higher level. In fact, most faucets in the house are restricted. That can make getting warm water a problem with a tankless system. Some will turn on with a higher volume, and stay on if it drops, some just plain won't turn on until the flow rate is within spec.

    They have their good points, but they also potentially take readjusting your habits and expectations. If you have a dishwasher that does not have a water heating capability, a tankless set to a low temp is useless. If you're trying to use hot water in a washing machine to sanitize things (and it can't heat it itself), your out of luck. If you live where the incoming water is quite cold parts of the year (and it could be all year if you have say a deep well), you may not get it warm enough.

    Then, throw in if your water is not soft, you must descale them on a regular basis or their performance drops way off.

    If you understand what and how they work, and are willing to size them properly for your needs, they are fine. Trying to get by with a low-end unit in most circumstances will take some readjustment of your habits and expectations.

    FWIW, adjusting the flow on a faucet does nothing to the pressure...it only adjusts the volume...the system pressure stays the same. Tankless heaters require a certain volume of flow to activate. Lots of people confuse volume with pressure.
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