Generally there is no fixed number of years, but you should observe its use at all times. If there are cracks in the water pipe, it should be replaced in time.
The theoretical lifespan of the heat collecting glass tube of the solar water heater is 15 years. After 15 years, the heat-absorbing coating effect of the heat-collecting glass tube will persist. not be good.
The insulating coating on the outside of the pipe is a black sponge coating. If the quality is good, it can be replaced every three years. If not, it should be replaced once a year.