Need a powerful tankless/Washington DC

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by sweetswededoc, Jan 2, 2008.

  1. sweetswededoc

    sweetswededoc New Member

    Messages:
    3
    I am switching to tankless and would like reccomendations on the best for us.
    Only 2 of us will be using but we have a 100 gallon tub and the shower is very high flow (no restrictor, high output, more than 3 gal/min). I need the highest flow rate I can get for residential). Why? Because My HUSBAND is high maintenence. And that tub has to be HOT, when he takes a bath!
  2. srdenny

    srdenny Plumbing Contractor

    Messages:
    361
    Location:
    SF Peninsula
  3. alternety

    alternety Like an engineer

    Messages:
    650
    Location:
    Washington
    You said you are switching to tankless - from what?

    If you are going to use a water heater for the rest of the house, how about a modulating condensing boiler and an indirect hot water tank. Kills a couple of birds with a fairly small number of stones. If you are only going to make DHW, you may not get into condensing mode a lot but you can get some very large boilers with a wide range of burn modulation.

    You can do this and have essentially infinite hot water wherever in the house you choose to use it. Size the boiler, indirect tank, and tank operating temperatures to handle peak loads on the tub. Use a tempering valve to reduce output DHW temps from the storage tank to safe levels.
  4. SteveW

    SteveW DIY Senior Member

    Messages:
    1,052
    Location:
    Omaha, NE
    Did you notice that on this very board there are currently 2 folks frustrated by their tankless WH problems? Not to mention Master Plumber Mark's ongoing concerns about these.

    If I were you, I would do a LOT of research before deciding to go with a tankless unit. Do a search on this site and you'll see some interesting opinions.
  5. sweetswededoc

    sweetswededoc New Member

    Messages:
    3
    Thanks so much for the time and great advice.
    I was looking at the Rinnai 98i initially, and was not aware of Noritz brand.
    We're switching from (believe it or not) an 80 gal electric tank. We recently gutted the house and modernized the bathrooms with a big tub and 2 nice showers and the electric tank does not cut it any more.
    Additionally, we have limited space. The house was built in 1870, so the mechanical closet was an added on room at the back of the house. It brely fits the furnace and an 80 gallon water heater. I would love to have the space for the boiler set up, but it just isnt there.
    Best New Year to All
    Judy
  6. Squ1rrel

    Squ1rrel New Member

    Messages:
    69
    Location:
    Texas
    Noritz does make a nice unit, but just a warning on the HOT showers....alot of tankless units have flow restrictors on them to reduce pressure if the correct temperature is not flowing out of them...so if you go over the maximum gpm in those cold DC winters, you won't be getting any pressure anywhere. The Noritz would probably be the best bet if you can get the gas.
  7. GrumpyPlumber

    GrumpyPlumber Licensed Grump

    Messages:
    1,404
    Location:
    Licensed Grump
    Yes, Noritz makes the highest GPM output of all.
    They're also very expensive.
    If you're looking to run two showers at the same time..and maybe one more faucet, a Rheem, Rinnai or Takagi would suffice.
    If the bath has a Roman spout with 6 GPM..you won't be able to run much else while filling.
    I'd suggest finding folks that already have them and asking.
  8. MG

    MG New Member

    Messages:
    160
    Location:
    Illinois - Near St. Louis
    That tub / shower setup sounds like a heck of a waste of water.
  9. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    You will have the best available hot water capacity if you can leave that 80 gallon electric in place and feed it with a gas-fired instant water heater.

    The instant heater will heat the makeup and you will get full capacity for a longer time. Also, you will not get temperature variations that can result from the instant water heater. You may need the extra capacity in the winter if your utility gets water from a surface water source such as the Potomac river.

    The electric heater will use power only when necesssary to maintain temperature or to make up for demand greater than the instant heater can handle. You could set it at a temperature a little lower than the instant heater setting, and it would use very little electricity unless your demand exceeded the capacity of the instant heater.
  10. rdtompki

    rdtompki New Member

    Messages:
    115
    Location:
    Iowa
    Depending upon your winter inlet water temperature a Noritz 69M might be sufficient. Rather than go with a very large, almost-commercial unit consider something like the 69M which can be run in parallel. A cable enables the two units to communicate.

    I'm very satisfied with my 69M, but I think tankless is a very individual decision. Tank WH are bullet-proof until they wear out and the standby costs are low. Tankless will supply 120 degree water continuously (or hotter) provided they are sized correctly. It's true that electronics can fail in which case you might not have hot water, but we've got electronics in almost every household appliance. If I apply the tankless vs. tank-type WH logic to furnaces we would all be burning wood or shoveling coal to heat our homes.

    I would recommend finding an installer who is familiar with the unit you like or installing the unit your plumber likes. Would be good if your installer stocked a few of the common parts.

    I assume you already have soft water either naturally or via a softener so de-scaling should not be required very often. Do get the bypass valves installed just in case.

    Rick
  11. therinnaiguy

    therinnaiguy New Member

    Messages:
    20
    Location:
    Massachusetts
    Tankless

    Check out the Rinnai Commercial tankless water heaters at www.foreverhotwater.com. Measure the temperature of your cold water (50 degrees or so on the coldest days) and compare it to what temperature water you want (typically 120 degrees), the difference between the two will give you the temperature rise (70 degree rise). Then look at the flow charts to see what model is best. Volume is not an issue, flow is!
  12. GrumpyPlumber

    GrumpyPlumber Licensed Grump

    Messages:
    1,404
    Location:
    Licensed Grump
    Problem with that is the tankless will likely have a flow restrictor to slow it when demand exeeds it's btu output rating....unless he uses a high output (Noritz).
    Putting it on the hot side might work, but not very efficient on the utility bill.
  13. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    I would never put an instant heater on the output side of a tank heater. I believe that is contrary to the manufacturers recommendations.

    Whatever the instant heater used, it has to pass the full hot-water demand of the user. The storage heater adds hot water supply and smooths out the temperature variations that can occur with instant heaters.

    The minimum flow of the Noritz is 0.7 GPM. With a storage heater you will get hot water at low flows that may occur with a lavatory faucet.

    Even with the Noritz 132 it will take about 13 minutes to fill the 100 gallon tub with 130 degree water from a 50 F supply. With the Rinnai 98i it would take 20 minutes. With an 80 gallon storage heater after the tankless the tub can be filled in 8 to 10 minutes.
Similar Threads: Need powerful
Forum Title Date
Plumbing Forum, Professional & DIY Advice, Tips & Need Opinion on a Soldered Joint Sep 6, 2014
Plumbing Forum, Professional & DIY Advice, Tips & Need help identifying shower cartridge Aug 25, 2014
Plumbing Forum, Professional & DIY Advice, Tips & Need help with shower faucet ID Aug 20, 2014
Plumbing Forum, Professional & DIY Advice, Tips & hot water heaters need to decommission chimney Aug 20, 2014
Plumbing Forum, Professional & DIY Advice, Tips & install buried pipe, pine needles Aug 18, 2014

Share This Page