The wait time to get hot water is primarily a function of the distance between the water heater and the point of use. The Rinnai is producing hot water within a few seconds of first water flow from a cold start. However you must purge all the cold water out of the pipe between the Rinnai and your point of use. For example if your kitchen sink is 50 feet and the water flow rate is 1 gallon per minute than it will take 90 seconds for hot water to reach your sink.

Having to wait for hot water after you open the tap is a pain. It also wastes water and energy. There are several ways to lessen this problem. First you should consider the placement of your water heater.  Because of their small size, Rinnai units can be placed in locations that you could never place a tank. If you can place your Rinnai close to your primary points of use such as your kitchen or master bath you will have the best of all alternatives.

If this is not possible you have 3 choices to eliminate the wait time or waste of waiting for hot water:

1.  You could use a re-circulating line that keeps hot water following through a loop in your water system and then through your Rinnai. This is a poor choice for two reasons. First it wastes a lot of energy (probably at least $100 / year). Second, it will shorten the life of your Rinnai and reduce your warranty.

2.  You could add a small electric hot water tank (only a few gallons) to the hot water side of your Rinnai and run a re-circulating loop through it. The Rinnai will still heat all the water and you will not shorten the life of your Rinnai or impact its warranty but you will still waste energy.  You could lessen the energy waste by running the pump on a timer.

3.  You could add a cold water line re-circulating system to your common points of use. This is a system that will circulate water from your Rinnai to a point of use by utilizing your cold water line as a return. This does not shorten the wait period for hot water but it does eliminate water waste and will not increase your energy cost like standard re-circulating systems.

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