Water leaking from plumbing connections at the heater inlet or outlet.

Safety first: Turn off the pump and relieve pressure at the filter before loosening any unions.

Steps to fix external leaks:

• Tighten unions: Hand-tighten the inlet and outlet union nuts. Do not overtighten with tools, which can crack fittings.
• Inspect O-rings: Disassemble unions and inspect O-rings for cracks or flattening. Replace with Raypak-compatible O-rings and lubricate lightly with silicone pool lube.
• Check glued joints: Inspect nearby PVC elbows and couplings for hairline cracks or poor glue joints. Cut out and re-plumb if necessary.
• Support piping: Add pipe supports or hangers to reduce stress on the heater headers.

Note: Always allow PVC glue joints to cure fully before restarting the system.