Simple pressureless solar water heater

Pressureless solar water heater

In this configuration the system is used as “add-on” to an existing water system with a boiler.
While not able to run around frost temperatures or below ( 0°C ), it is a easy and comfortable way to produce hot water.

The collector/tank was mounted onto 8cm X 8cm wooden beams with proper screws.
For easy acces, a position on a “half roof” was choosen. The installation took about one day (with some modifications to the support frame).
The water installation is in parallel with the existing hot water boiler.

As connection 16mm semi flexible pipe(PEX – AL Henco) was choosen using compression fittings.

The device is an unpressurized tank (160L model with 18 vacuum tubes) with a heat exchanger coil. Overall the system does not need much space, the installation is pretty straight forward and the price is relative low.


-Does not need much space, very compact build.
-Since the tank is pressurless it has a basic overtemperature protection (evaporation cooling effect)
-Easy assembling/plumming
-Can go ruffly 2days with the 160Ltank and 3 people using it (without the sun shining)
-About 20 year life time expectancy
-Easy to integrate into existing hot water heating systems
-Higher efficiency compared to heatpiped models
-Needs about 6h of good sunshine to heat it up
-Better low shunshine efficiency compared to flat panel termal heater


-does not support freezing temperatures(has to be drained)
-hard water can cause a few issues down the road

Special thanks to OffGridEnclave community member Dank_meme_kong for providing Pics and Infos to present this as Project.
If you would like to see more pictures or read up on details of the build join our community discord server.