It takes a while for the water to heat going to the tankless water heater and in doing that, a lot of water gets wasted. Is there such a thing as a pre-heat switch that would start the heating process prior to the water flow activating it? Is there anything that would reduce the amount of water being wasted while waiting for it to get hot enough (like for a shower)?

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    When you had a tanked heater, are you sure it didn't also do this? Commented Dec 7, 2018 at 23:17

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That would be a tanked system with a recirculation loop but what you save on water you waste in power consumption. The best alternitive would to purchase a point of use heater they are smaller and lower flow than the whole house model but other than that not running without flow is how these tankless units save $.

  • I wasn't sure whether or not recirc. loops could work with a tankless. Thinking about it... Commented Dec 7, 2018 at 23:07
  • I don't see why it wouldn't. It would just constantly keep the water at X temperature. Keep in mind both the heater (when the water cools down) and pump would be running 24/7 and you'd have to run a second pipe from that faucet back to the heater. Would it be worth the installation, upkeep and power costs? Commented Dec 8, 2018 at 1:36
  • @hazardousglitch there are systems out there that do this using the existing plumbing and a pump, the problem with trying to do it with a tankless they heat at a massive rate so it would be cheaper to go back to a tanked and recirculation system. I don't know off all tankless systems work the way mine is but it requires a delta of pressure from the inlet to outlet to heat. With recirculation systems there would not be enough pressure differential but as I said it would cost way more even if it would work.
    – Ed Beal
    Commented Dec 8, 2018 at 16:51

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