I recently moved into a house that has the Rinnai REU-V2520FFU-US hot water heater. Unless the faucets are turned all the way to the hottest point I experience temperature fluctuations from hot to cold in all showers/sinks that have single faucets. The tubs where there are 2 seperate faucets for hot/cold seem to be fine. I have tried replacing the shower heads to increase flow but the fluctuation is still occuring. Any suggestions?