I'll take it out and try this- would be an easy step before buying a new one since I need to take it out anyways. Thanks for the idea

I took the cover off, flipped it around and couldn't find anything, but I didn't look at a manual- Ill give it a shot, thanks.

House was built in 1994, ive been here for 6 years. Doing a small bathroom remodel. I put a double sink in where there was a single sink in place- Noticed I started getting a gargling from the sink drain, which was not present before; happens when I run both the sinks and the bath. Doing research, it looks like it can be caused by a clogged vent; however, I do not see a vent for my sink.

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1. Is the gargling potentially caused because by the double sink? Odd that this popped up now and not before.

2. What does adding a vent look like? Looks like it is a major task