I have had Rheem tankless water heaters before because their reputation for quality products is well kown. For those first-time users be reminded that there is a learning curve in using tankless water heaters. I tell people to make small adjustments when bringing the water up to their desired temperature. Note the approximate location of the adjustment lever and when getting into the shower move the lever to that location and let the water run for about 15-30 seconds to reach the desired temperature. Then you can make minor adjustments while in the shower. Making major changes to the lever position can fool the sensors in the water heater and add too much cold water to the water stream giving the user a shock of cold water. Remember- SMALL ADJUSTMENTS!