Rinnai tankless water heaters work perfectly as long as they are installed properly and undergo an occassional “flush out” to remove mineral scale from the inside of the heat exchanger. The tankless flush is a simple procedure and if you are a slightly mechanically-inclined handy-person, give it a shot.
Here’s a video from Rinnai that explains the flush out procedure. If you prefer to have a company to service the tankless unit and are in the Metro Atlanta area, we highly recommend calling us.