Solar fluid should be changed every 3 to 5 years otherwise the system will start to lose protection from the corrosion inhibitors. The fluid can become acidic causing pitting and pin holes and the antifreeze effectiveness is reduced.
Check the system pressure gauge every month. It shouldn’t drop below 0.5bar. This is the number one indication that there is a problem with your system.
At the end of March March, change the boiler hot water timing to just once per day (from 16:00 to 17:00) and on the next sunny day turn the boiler off to confirm that the solar system is actually heating the water.
