Valves (one way valve, air check valves, non-return valves) in the air blower system are predominantly used to stop water flooding back to the electrical hot tub blower.
1-1/2" socket x 1-1/2" socket with 1/4lb spring for Blower lines
2" spiggot x 2" spiggot with 1/4lb spring for Blower lines.