We would like to say that it is not advisable to drink solar-heated water. Doctors have been skeptical about drinking the water as they may have minerals from the pipes. Also, the ultraviolet rays from the sun are not seen in the best way. But, it is okay to utilize the hot water for other household needs.  It is also advised to drain the tank from time to time, or else the same water may get recycled. One can use it as bath water or for washing clothes. In turn, having a solar water heater at your home provides a cleaner and better environment. So, do not think much about it.