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Mixing Valve Question

We have a Weil McClain 880 Series Boiler with internal tankless water heater and a 119 gallon SuperStor hot water storage tank as well to make sure we can keep up with demand (There are 16 apartments being served). We currently have a Watts Mixing valve with a brass body that we believe is defective. We have already rebuilt it and it is not working correctly again.

We want to replace the entire mixing valve. We have a honeywell in another building that works ok, but this building has always had Watts. We've heard that Taco makes a decent one too. Should we stick with Watts or go with something else? What brands do you recommend?

Thanks in advance for any advice and help.


  • heatpro02920
    heatpro02920 Member Posts: 991
    I use Taco and not because they are local...

    Taco series 5000 works very well, I use them for everything {DHW, radiant mixing, diverting, ect} so its easy to stock the one type, I stock 1/2", 3/4", and 1" Im not sure if they make other sizes I doubt it, they are expensive but do it once vs twice and you saved money... I also have 1/2" and 3/4" watts 70af but thats because they are so popular and keep them for direct replacements...

    But anyway Taco 5000's for the gold......
  • pipeking
    pipeking Member Posts: 252
    what size piping

    do u have. as heat pro said i also use taco 5000 for the same applacations, and keep the watts for pennie pinchers. BUT, on large scale mixing, like appatments,hotels,and other stuff like that i like leonard mixing valves, they specialize in water temp. control and their product is the best for large scale. you would be considered large scale haveing 16 appartments. what is your flow requirments, what does each unit have for fixtures? if i was to guess 1bath+kitchen so a max of 3-4gpm of hot water. so 16x4=64gpm, are there any other hot water needs, public washroom,pool house,ect... so u need some thing that can have an output of 1-2gpm (in the rare case only 1 unit is using water) - 64+gpm. i would go with this one>>>http://www.leonardvalve.com/productdetails.asp?i=4179&fa=1&productname=Exposed-Assembly&model=TM-820-RF
  • Jeremy_16
    Jeremy_16 Member Posts: 113
    Thanks for the responses

    Attached to this post is a picture of the mixing valve we currently have. It's a Watts N170L-M2. The mixed water coming out going to a 1 inch pipe. I think the inlets for hot and cold are also 1 inch.

    In each of the 16 apartments there is one bathroom and one kitchen (all have dishwashers if that matters). There is also one slop sink and 2 washing machines in the basement that the entire building shares.

    Is there any particular feature that a mixing valve we buy should definitely have?

    I'll check out the Taco series 5000 and Leonard Valve that you both suggested. Thanks.
  • pipeking
    pipeking Member Posts: 252
    the watts

    thats installed now has a min flow rate of 8gpm and a max of i think 65gpm. the taco 5000 1" has a min flow of .5gpm and a max of i think 25gpm. the leonard that i recommended has a min of 1gpm and a max of 80gpm. the taco 5000 is to small for your app. the lenard might be overkill, but i can't say without doing my own calculations. u want to have happy tenents, and if they never once have a complaint about the hot water then thats what u strive for.

    i want to assume that u have a recirc on the dhw, thats how u get by with the watts. 8gpm is to high and is wasting energy. go to the leonerd website and they have single mixing valves that might wok for u.
  • SWEI
    SWEI Member Posts: 7,356

    6-500 is also worth a look.  The minimum flow rates go way down with continuous recirc.  I use B&G/Laing ecocirc e series pumps and dial down the flow rate so there's no overheating. 
  • icesailor
    icesailor Member Posts: 7,265
    edited February 2013

    In my opinion, that valve is wrong for your application. A Watts N170L-m2 is a "Hot Water Extender" valve. It is NOT a thermostatic mixer for careful control of potable domestic hot water. It will not control hot water temperatures if the hot water is circulated. You need a true, thermostatic hot water valve, properly sized to the load/use.

    Hot water extender valves, even if they are thermostatic types are not the same as a Symmons or Leonard. Both are true anti-scald devices and will pay for themselves quickly when you can then circulate 120 degree water throughout the complex instead of water of whatever temperature the valve will deliver. It is the varying flow rates that make those valves so bad.

    You need a valve like this one.

  • Jeremy_16
    Jeremy_16 Member Posts: 113
    Clarification and more questions:

    Hey All,

    Thanks for the responses. To Clarify: We do not have a recirc line for the building. The tank has a line that runs back to the tankless coil in the boiler to keep the water in the storage tank at temp, but that's it.

    I'm really not sure what maximum flow rate we need. We have another 16 unit building with a Honeywell AM-1 series mixing valve and I think the maximum flow rate is 25 gpm, but the mixing valve we have now at this building is 58 or 64 gpm (or so I'm told by my plumber). No one has complained about insufficient hot water at the other building, but I'm concerned about putting in a mixing valve with only 25 gpm if the one we have now is so much higher.

    Icesailer, the mixing valve that's there now was put in a long time ago. You may be right about it being the wrong type. I don't plan on replacing it with the same type of valve, but just curious if it is the right use now that you know we don't have a recirc line for the building or it's still the wrong kind? How is a hot water extending valve different as long as you can set the temperature?

    One other valve that's been recommended to me is Holby. Do any of you have any strong feelings about that company? So far everyone here seems to really like Leonard and Taco. I had heard of Taco before, but never Leonard.

    What's the difference between these valves with and without checkvalves? Is it better to have one with the checkvalves?

    Thanks again!
This discussion has been closed.