High air pressure coming up sink(commercial)

[grantsmurphy]

Larger 2 story 40+ year old building. I am the maintenance person for property.

It has a vent outside, (attached picture) although not much higher then the sink inside, in fact now that I think about it, it's probably lower.

I replaced the existing vent with that black one. The main drain line for that building backed up about 2 weeks ago before this started happening, I snaked it with a 100ft line.

Plumbing is my least knowledgeable area, any advice would be greatly appreciated.

I am thinking maybe this vent is too low.


Edit: this is the last drain in the entire line. I don't know if that matters. This is also the only place it's happening.

 

[Twowaxhack]

You need a real vent. That’s an air admittance valve.

 

[grantsmurphy]

You need a real vent. That’s an air admittance valve.

Are they both air admittance valves? Or did I get the wrong part? The black one is the replacement.

 

[TomFOhio]

Around here the black one we call cheater vents. Their used for mobile homes. Try taking the black vent
out and see if the water shoots then. If it doesn't then you know the vent needs extended

 

[grantsmurphy]

Around here the black one we call cheater vents. Their used for mobile homes. Try taking the black vent
out and see if the water shoots then. If it doesn't then you know the vent needs extended

When I would remove the original vent, the water would drain. That's why I was just guessing the vent was bad some how. I didn't realize it was an actual valve.

 

[Twowaxhack]

Air admittance valves let air into the system. You need to let air out.

The black one is technically a mechanical vent. It has a spring.

The studor vent is not a mechanical vent, it has a diaphragm that’s acted on by air pressure.

The black vents are only legal in Mexico and Iraq.

 

[grantsmurphy]

Thanks for the help everyone!