content: My well produces 6 GPM. I have a tankless water heater and I waste water until the hot water arrives. I put the 4 gal. ariston in series with the water heater for the downstairs shower-it works great- instant hot water. I also put a 2 gal. ariston under the kitchen sink. They both save us water. The tankless water heater heats on demand so every time you turn the valve you fire up the water heater. In the kitchen I hooked the ariston to the cold water (it takes too long for hot water) Works fine for me since I do most of the dishes by hand. The fridge has cold water for drinking. These heaters are easy to install so it can be changed in about 5 min. Bill CA.