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130 degree water is the max inlet water temp for a Rinnai so you risk damaging the Rinnai with water that hot. The water won't get hotter since the Rinnai burners won't fire when the water temp is above the set point. Off hand this is the case (inlet water temp etc) with all tankless heaters. There is a workaround if you're not turned off by the complexity. You could put a strap on aquastat on the line out of your tank and have 2 solenoids down stream. If water temp drops below say 120 the aquastat would open the valve to the Rinnai. Above 120 and it sends it directly to the house.