Anyone know what the adjusting screw on back of the valve does? Does it make it louder? Thanks for any info.

 

It does not make it louder, its to tighten the spring pressure

 

yeah, it doesn't make it louder. I have one and I use it to adjust the sensitivity of the spring, like to make it open easier under different conditions...If you really don't understand then think of it like this....the looser you adjust it the easier it will open and the more sound you will hear as far as the tamberine whistle sound goes....