Water flow through the heater seems restricted; high filter pressure when heater is in line.

Safety first: Turn off pump and power, and relieve system pressure before opening plumbing.

• Valve positions: Confirm all valves to and from the heater are fully open and that any bypass is correctly adjusted per Heat Siphon instructions.
• Backwash/clean filter: Ensure the filter is clean to rule out filter‑related pressure issues.
• Inspect manifold: Remove union connections and inspect the heater’s water manifold for debris or scale. Flush as needed.
• Descale if needed: If scale buildup is suspected inside the titanium coil, follow Heat Siphon’s chemical cleaning procedure or have a professional perform a circulation descaling.