Tank to Tankless/Instant Hotwater System

xdivino on 18/11/2022 - 15:26

My Hot tank currently showing leaks and yellowing waters, it's hit that 11-12 age range so it's time to yeet it

I've downsized and hot water use would be only for bath/shower at most, dishwasher is cold and washing machine is cold water connected only so it's really just bath/shower, bath sink and kitchen sink.

I"ve been looking at tankless instant hot water systems, and keen to go that way as the Tank sits currently in my laundry and takes up a heap of space and is likely way overkill for the use I have.

Is the first port of call an electrician, a plumber or can hot water installers do both needs?
Also, what's peoples usual go to for this, google search or just word of mouth recommendations etc?

Home & Garden Hot Water System

Comments

  • GG57 on 18/11/2022 - 15:34
    +3

    Also, what's peoples usual go to for this, google search or just word of mouth recommendations etc?

    Ask OzBargain, obviously.

  • SkMed on 18/11/2022 - 15:38
    -1

    Do you have 3 phase power? If not and you live in the colder parts of Aus you can forget about it. Already looked into it myself and had to abandon it as the water will only get lukewarm in cooler climate without 3 phase in Melbourne.

    • xdivino on 18/11/2022 - 15:43

      Sydney so not crazy cold but not sure on the power as an older apartment..
      about to have an electrician thru the place to wire up a garage lights/power etc. so could prob see if they can swing upgrading things or not.. idk..

      • SkMed on 18/11/2022 - 17:02

        I think you'd still end up with some lukewarm water if you dont have 3 phase. I was told really only QLD/NT can get away with it all year round.

        • Carbon Door on 20/11/2022 - 08:00

          Electric hot water system?

          • SkMed on 20/11/2022 - 08:24

            @Carbon Door: Sorry, yeah, specifically I stat electric hot water system, gas probably fine

  • BewareOfThe Dog on 18/11/2022 - 15:42

    We have 'instant' gas hot water, and it takes about 1 minute to get hot. Only leaves 2 to 3minutes to have a shower.

    • Archi on 18/11/2022 - 16:04
      +1

      That's not instant… its continuous flow.

    • fredblogs on 23/05/2023 - 18:42

      it goes cold after 3 minutes?

  • AndyC1 on 18/11/2022 - 15:43
    -1

    Recommend a heat pump instead of instant electrical hotwater and then use hot and cold for the dish washer and cloths washing as you will save money.

    On the flip side heat pumps are more expensive to buy, but running costs are allot cheaper.

    • xdivino on 18/11/2022 - 16:06

      Not sure if there’s tankless heat pump
      Trying to downsize and free up space more so than doing another tank

  • JimB on 18/11/2022 - 16:33

    Do you have gas?

    • xdivino on 18/11/2022 - 16:34

      no joy, my street doesn't have it

      • JimB on 18/11/2022 - 16:46
        +1

        I doubt tankless will work for you then.

        • xdivino on 18/11/2022 - 16:55

          Electric Tankless?

          • JimB on 18/11/2022 - 17:48

            @xdivino: Electric can’t heat it fast enough.

            • GordonD on 18/11/2022 - 18:13

              @JimB: Thought 3 phase could. It just takes a lot of power. But wouldn't expect a unit, especially an older one, to have 3 phase power.

              • JimB on 21/11/2022 - 09:35

                @GordonD: You're right, I think 3 phase can do it. But as you said, very unlikely an older unit will have 3 phase

  • outlander on 18/11/2022 - 18:50

    Let's try some math:

    It takes 4.2 joules of energy to heat 1ml of water 1 degree. If you live in Melbourne, your cold water might get down to 7c in winter. When you shower, you generally shower at 35-42 degrees. Going to assume the water heater is right above the shower so we don't have to worry about transmission losses. Heating from 7c to 42c is a 35 degree differential. If you shower at full pressure using a water saving shower head, you're going through 10L per minute, or 166ml per second. To heat 166ml of water by 35 degrees requires 24.4kJ of energy, every second.

    A watt hour is equal to 1 joule per second, so 24.4kJ per second requires a 24.4KW heater, assuming perfect efficiency. Most ordinary houses have a fuse of 60amps, which means the most you can pull at once before it breaks is 14.4Kw. You can get it upgraded to as high as 100amps I think, but even that only allows for 24Kw.

    I'd say based on that, that pure electric is out, unless you can go to 3 phase or want to use extreme water saving showerheads/only shower in the summer months.

    Alternatively, a compromise could be to switch to a smaller tank plus an electric instantaneous system. A 50L tank has a much smaller footprint than most conventional water heaters. People even fit them under the sink. With 50L stored at 70 degrees, you would normally only be able to shower for around 10 minutes before the hot water was all used up and the shower went cold, with 4 hours needed to fully recharge. But if you were to temper the water coming out of the hot water tank to 30c, and then use an instant 10kw to boost it the rest of the way, you could get 3x the amount of hot water from the tank, enough for two people to shower back to back.

    Disclaimer: numbers are all very rough and likely to be wrong as I don't do always do math so good]

  • Sinnerator on 19/11/2022 - 08:02

    How often do you drain your current hot water system, every 3 months?

Login or Join to leave a comment
Login Join