Most people who live in a single family dwelling buy a forty gallon water heater, which is more than ample for a family of four of five people. In order to figure out what size water tank you really need though, you have to take into consideration all of the uses for hot water that you might have. This is especially important if you own a multi-family building like an apartment complex. It is especially important that if you are the president of a local condo association to take the time to have a professional estimate of how much hot water the building will use in order for you to buy the right hot water tank.
The best way to figure out how big the water heater that you might need is to think about all of the uses for hot water that are necessary. Here are some questions to ask yourself before you call a local plumber to install the hot water heater that is right for you.
How many bathrooms do you have? How many people live in your home or in your building? What are the size and water output of the shower heads? How often is the dishwasher used? (In the case of a multiple unit building, you will have to consider how many units have dishwashers and how often they use them.)
Washing machines are also a consideration. In the case of a single family home, you have to think about how many people use it. If you have an apartment building with several tenants, you may need a larger unit to accommodate people who use more hot water when they wash their clothes.
The last thing to consider is the dishwasher. If you live in a single family home and run it once a day, a 40 gallon tank will suffice. However, if you own a commercial property like an apartment building or a restaurant, you will need to talk to an experienced plumber to figure out what size water heater you need.