Jerry Peck
Being as this setup is for maximum gallonage of hot water, the two tanks should be set to the same temperature.
However, being as there are only two of you and maximum gallonage is not needed, just crank the first water heater down to around 100° f. If you ever need the extra gallonage capacity, at least this will not be putting ‘cold’ water into the second tank, it will already be ‘warm’ and will not take as much time to heat up.
