There are a few ways to clean a solar water heater. You can either use a vacuum cleaner with the hose attachment, or you can use a brush and some dish soap. If there is any dirt or grime build-up on the panels, you can use a toothbrush to scrub it off. Make sure to rinse off the panels thoroughly afterwards.

There is no one-size-fits-all answer to this question, as the best way to clean a solar water heater may vary depending on the specific model and brand. However, some general tips on how to clean a solar water heater include checking for leaks, cleaning the filters, and cleaning the panels. It is also important to make sure that there is adequate insulation around the system so that it can operate at peak efficiency.