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I live in a three-story townhouse and I have a Navien tankless water heater installed in my first floor garage. When I turn on hot water on the first floor, I’m able to get hot water pretty quickly, in 10 seconds or so.

However, when I do the same on the second and third floor, it takes extremely long to get hot water (sometimes up to a minute). What could be a possible reason for this? Water in my area is extremely hard, and I haven’t been using a proper water soften. Could this have clogged a pipe going to second and third floor for hot water? Water pressure for both hot and cold water is great on both floors, so I’m not sure if this is water heater or pipes. I haven’t flushed the water heater for the past three years, if this helps.

I feel the delay has become worse in the pst two years. Any help would be greatly appreciated!

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  • Water gets cool/cold in pipes. The more pipe distance, the more cold water needs to get out of pipe before you get hot water.
    – crip659
    Commented Sep 21, 2021 at 9:47

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It is simply that you are further away from the source of hot water. You need to purge all of the standing water in the pipes leading to the second/third floor from the water heater in your garage before you get to the hot water from your water heater.

If you are allowed to make modifications, you could have a recirculation pump installed to constantly recirculate the hot water through the pipes which would waste more energy to heat the water constantly, but also would mean nearly instant hot water everywhere and less water wasted before you get hot water.

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  • Another option would be to put a small instant heater in each bathroom on the upper floors. This would heat the cool water in the hot water pipes just before the point of use, giving you "instant" hot water. Once the hot water from the main heater reaches the small heaters, they turn off because the inlet temp is already at or above their set point.
    – FreeMan
    Commented Sep 21, 2021 at 11:32
  • Another way to solve your stated problem is with patience. Above suggestions will help and a water softener will not solve this problem. However if you have hard water, a softener will increase the life and reduce maintenance of your water heater, as well as other things like your tea kettle, iron, etc.
    – jay613
    Commented Sep 21, 2021 at 11:47
  • I have recirculation pump installed at the point farthest from the on-demand water heater. It is triggered by a push-button and it runs until it detects hot water in the pipe. No water has to be wasted because it simply recirculates the cold water back to the heater. It required running a low-voltage wire from the pump to a button on the wall and a return line for the cold water to go back to the heater. Don't use the existing cold water line for the return line or you will get warm water from your cold faucet.
    – Stephen Daddona
    Commented Sep 21, 2021 at 16:03
  • Thanks, everyone for your comments! I think I can live with it (was just curious if this was normal).
    – Brian C
    Commented Sep 21, 2021 at 19:18
  • Do note though that recirculation pumps waste heat: the hot water in the pipes heats the rooms they pass through all the time, causing your heater to run more (and your air conditioning if you have it ). Good insulation helps, and is a requirement in many places, but perfect insulation isn't possible in practice (or in theory).
    – Chris H
    Commented Sep 22, 2021 at 10:28

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