1. Visually Check pipework for any leaks. This will be particularly important if there has been any drop in system pressure.
2. Check the blow off vessel for any expelled fluid.
3. If any system performance issues have been noticed, confirm there is no airlock in the system (ie check that any available heat from the collector is being delivered to the cylinder). You will need a sunny day to do this.
4. It is generally recommended that the glycol in a system is replaced every 5 years. However, if you have any suspicion that the system could have been under stagnation for any period of time, you should test the fluid for its antifreeze characteristics with a refractometer and pH levels with litmus paper during the service. For more details, consult the attached service schedule.