[retiredguy123]

Originally Posted by Justputt

Two considerations with tank or tankless, without a continuous recirculation pump, there's no "instant hot water." First, a tankless heater's heat exchanger needs to get up to temperature (120F, for most), even if gas. If you put a pan of water on the gas stove and turn it on, the water isn't instantly hot. Second, regardless of the source (tank or tankless), the HW lines are full of cold water that must be displaced. In a recirculation system, it sends the water back to the tank or tankless heater, as applicable. Recirculation is with a separate return pipe OR a thermal bypass valve (several good YouTube DIY videos) located at the sink/shower/tub which send the "unheated" water to the cold-water line and won't shunt water to the HW faucet until it is "hot." I just ran a quick test using my guest bathtub, which I think is furthest from the tankless heater. It took 1 minute to get warm enough at the tube faucet (showerhead flow rate would be lower and usually takes 2 minutes), and it dispensed 10 qt (measured with a 10 qt bucket) in that time. Where I used to work (hospital), they ran the recirculation pump continuously (not cost effective for homes!), so they did have instant hot water. I looked at all the DYI stuff this past summer and decided the cost wasn't worth it since all I was saving was 10 qt of water, as it still takes the same amount of time to heat the water at the source and cycle the cold water from the lines. Additionally, timers are fine, but you're either going to set the timer to start every day at say 7 a.m. or set it to run for a couple minutes every time you flick a switch somewhere in your house. To me, that's just a hassle. IMO, flip the HW on, hit the head or brush your teeth and that should be good enough to at least have comfortable warm water to start.

Mine takes less than a minute to get hot water to the shower. But, I have found that, if you can't wait to take a shower, turning on the sink faucet and the shower at the same time will reduce the wait time to less than 30 seconds.