What is it

[MyBudy]

Can any one please help me? I have a custom acrylic tank and on the bottom of the tank there is two fittings, one is a bulkhead that is plumed to a pump, the other looks like a bulkhead but it has a air hose from the air pump and two thumb screws that I can adjust the flow of air (what is this thing called and where can I buy a new one) if I shut the air off it starts to leak.

thanks for the help

 

[OrangeCones]

Posting a picture would help, but sounds like a saltwater tank set-up. The air would run a skimmer.

 

[wananwu]

does it leak where it connects to the tank or does the back flow valve not do what its supposed too