An invoice, bill or tab is a commercial document issued by a seller to a buyer, relating to a sale transaction and indicating the products, quantities, and agreed prices for products or services the seller had provided the buyer. Payment terms are usually stated on the invoice.
When a vent is less than 10 feet high, the vent should be at least as large as the flue collar outlet.b) Vents for draft hoods or flue collars 12 inches in diameter or less should NOT be reduced more than one pipe size.
Vents admit air into the pipes that helps equalize the air pressure in the pipes to prevent blowback and siphoning of the water seal in the trap. All fixtures need one, and only one, trap that is set level. Fixtures with an internal trap, like a toilet, do not need and should not have a separate trap.