The best way to position your solar water heater is by finding the south side of your house. The sun rises in the east and sets in the west, so having your solar panels on the south side of your house will get the most direct sunlight exposure. However, if you can't have them on the south side then try to have them on an east-west axis so they'll still get some good sun exposure throughout the day.

That depends on a number of factors, such as your location (sunshine intensity, latitude), your climate (solar radiation), and the size and type of solar water heater you're using. Generally speaking, south-facing roofs receive the most sunlight throughout the day, so they're a good option for installing solar panels. East- and west-facing roofs are also good options, but they won't get as much sun as south-facing roofs.