Due to the different layout of homes, distances from the water heater to the sinks/showers/etc. will vary. It is important to check the water temperatures at each water dispensing location. Some homes may have very small variances in water temperature, some may be considerable.  This may be due to how the pipes are run through the house or the integrity of insulation used. A sink located across the house from the water heater may be at 115 degrees, but a shower closer to the water heater may be at 125 degrees. For good readings, run faucets and shower heads for at least 5 minutes, taking temperature readings every two minutes, per location. Water temperature must be between 105 degrees and 120 degrees Fahrenheit.