The ones that are in the pictures of the article you sent are actually effective, the ones that we use that’s acceptable by code still is just a 12 inch pipe with a cap. They don’t really work though because over time the air pockets full up with water so they basically become useless.
The ones that are in the pictures of the article you sent are actually effective, the ones that we use that’s acceptable by code still is just a 12 inch pipe with a cap. They don’t really work though because over time the air pockets full up with water so they basically become useless.