thanks for the reply
so if One US gallon is 0.133681 cubic feet my box would need to be about 5.34724 cubic feet.... no wait i need to fit in the heat exchangers too........... anyone know about how many feet of exchanger tubing i would need ?
my old water heater the tank was 40 gallons so thinking about going with a 40 gallon this time
i have room for a box size of 4 feet by 2 feet
may go with copper tubing for the exchanger not sure what size exchanger i will need might fill the box mostly full or half way full with the heat exchanger
the geyser heat pump water heater has a water pump in it to pump the water from the box to the geyser unit and back to the box then the tap water will flow thru the exchanger and pick up heat on the way to my shower