I have installed a Rheem 110L water heater on its side. We have gravity fed water from a tank on the roof . The tank is not high enough to fill the water heater vertically , so I laid the water heater on its side, but Im only getting 80 degree water, and it has a new thermostat and element. What can I do? It is mounted on the roof next to the water tank . The unit has the tubiing on the bottom . I live in Lima, Peru I`