John,

I see those all the time. The builder installs them wrong and tells the homeowner that it is installed to pour bleach every 6 month in-order to clean out the trap and other nasties. In reality, the darn thing was installed before the trap and just wrong.

The thing to do *IS* go ahead and cap that one off (with a removable cap) and install a vent after the trap.

__________________
"If con is the opposite of pro, is Congress the opposite of progress?"
Richard Rushing, HCRI
Duncanville, Tx.