solar water heater with plastic bottles

How to do big plastic water heater (PET)bottles.
There is a 3 in each bottle.
4mm dropper 5 m.
This heater uses the greenhouse effect in the bottle.
It\'s like the heat of a car in the sun in summer.
Because when the circuit stops, the water inside the water pipe will heat more, it is a good idea to use the timer with I. e.
1 minute, 1 minute.
This will also protect the pump motor from excessive heating.
With a small water pump, the water cycle, the temperature rises.
It is best to use a 12 v dc motor pump connected to several solar cells.
In order to concentrate more heat in the bottle, you can also try pasting a piece of aluminum foil.
The solar water heater is scalable, so you can connect more bottles and bottle groups to heat the pool.