It takes a few minutes for my tankless water heater to warm up, so we end up wasting a lot of water in our shower. Is there a way to avoid this? A friend mentioned a “comfort valve” or something? What is it and how does it work? Or is there another solution? Thx!
Look into recirculating pumps. https://chilipeppersales.com
I have one of these, I put it on the slowest to heat/furthest sink. I put a 200uF capacitor on the trigger wires and plugged it in to a smart outlet. I added an automation in homeassistant to turn that outlet off after 3min whenever it gets cycled on. Whenever we need hot water we just toggle the button in HA and the showers all have hot water in <90s and <1L.