System is not working.
Pump is defective.
Controller was set on Auto. Pump operation indicator was on. Pump was plugged to controller. No hum, no vibration, no heat. Plugged pump directly into 100V receptacle. Pump did not come on. Pump area indicated residue from previous leak.
Leak at fitting below return ball valve/check valve.
Leak at pipe fittings.
Anti scald valve was stuck.
Gaps between copper piping and insulation in vertical pipe sections at roof provide opening for water penetration. Especially at bends where pipe runs go from horizontal to vertical. Insulation has deteriorated at bends and exposed piping.
Long pipe runs lying on roof allow leaves to accumulate.
Screws used to mount struts to collector are rusting.
Air vent is in good shape. No calcification at outlet port – as is often the case.