A re-sealing trap is designed to allow air to pass through the water seal under negative pressure but will retain sufficient water to ensure the minimum depth of seal is retained. Whereas an anti-siphon trap has a small mechanical valve that opens under negative pressure. Both versions will break the siphonic action thus protecting the water seal. Note, the resealing trap may be noisy. For more details see relevant pages on the website or catalogue. View anti-syphon and resealing traps.