Plunger valve - small knob

[sputterbug10]

I have a question about these intex plunger valves. There is a small knob next to the nut that screws it on to the pool. What is that used for?

 

[MikeInNH]

Kinda looks like it is there to allow you to get air out of the system.

 

[tamaralemus]

it is actually an air valve that sucks air in if the vacuum is too strong for the amount of water coming out (like if have a stronger pump than what came with the pool, or if the strainer basket gets blocked). I have to cover mine when vacuuming otherwise my pump loses suction from the air coming in......

 

[sputterbug10]

thank you. Mine was loose and I tightened it but I wondered if maybe I shouldn't have