Home Valves, Vessels and Control Vessels Distribution Systems Adaptors and Closures Pentair A-AV-150PP Aeration Valve 1/2 BSP - 1 1/2 BSP for 14 - 63 Vessels (vacuum Breaker)
If there is no aeration valve, the warranty is voided in case of vacuum leading to tank break.Aeration valve is a safety device to prevent this.