Bilge Pump Anti-Siphon Loop

This 2002 IP-420 experienced regular siphoning of seawater through the bilge pump stern port under sail and power mostly during following-sea conditions. Plumbing was unaltered before improvements to correct conditions in 2005. Siphoning was revealed after the bilge flooded during a passage in which children playing on the cabin floor accidentally knocked the pump switch into the off position.