In doing home renovations, we've added a new bathroom on a third floor, a new sink (where there was previously only one) in the second floor master bath, a new island sink and a new bar sink on the main floor (where there was previously only one sink in the kitchen)and a new second floor laundry. We are a family of five, which includes three teenagers.

The house has a 40 gallon gas hot water tank that's been in place with no problems as long as we've owned the house (15 years). Anticipating we'll need more hot water, my builder and his plumber suggested replacing the existing hot water tank with a 75 gallon tank. In talking with my plumbing supply house, the sales person suggested purchasing two 50 gallon tanks for roughly the same cost as one 75 gallon tank and gaining an additional 25 gallon capacity. Of course, he does not know the cost of plumbing the two tanks in tandem. Another option would be to keep the old tank and add a new 50 gallon tank in tandem with it. Any suggestions, thoughts or comments on what would be the best way to go would be appreciated. Thanks.