The best thing we have ever added to our houses and hot water you could boil an egg in.
We have only applied solar heating to our new houses and during the contruction as the systems use copper pipes. I am not sure whether normal plastic water pipes can handle the connection to one of these solar heaters.
Most large retail outlets sell this technology and it would be best to have an engineer visit you first and to have a look at the job, assess what type and size of unit you need and then to quote accordingly. As these units are normally roof mounted they must check your roof structure to make sure it can stand the weight of the working unit.
I have found the Thai manufactured systems are very suitable so no need to purchase an imported one and good luck.