Controller displays AIR or AIRLOCK and solar heating cycles on and off; gurgling noises are heard from the roof.

Safety first: Turn off the pump before opening any plumbing or unions. Use caution on ladders and roofs.

• Inspect vacuum relief valve: Locate the vacuum relief valve at the top of the Heliocol array. Ensure it is installed vertically and not clogged with debris. Replace if stuck closed or leaking.
• Check plumbing slope: Verify that the supply and return lines to the roof have a continuous upward slope to the array and downward slope back to the equipment. Correct any low spots that trap air where practical.
• Increase pump speed: For variable-speed pumps, temporarily increase speed when solar starts to help purge air from the panels, then reduce to normal operating speed.
• Check for suction leaks: Inspect pump lid O-ring, suction unions, and valves for air leaks that can introduce bubbles into the system. Lubricate or replace O-rings as needed.
• Bleed air manually: With the pump running, carefully crack open a high-point union or manual air bleed on the roof until water flows steadily, then retighten.