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!
They could install a small - around 2 gallon - electric water heater near the shower. I have a similar problem in my kitchen and it was solved quite cheaply by putting one of those under the sink.