Double Vanity Drain Pipe Size

This diagram of a typical dwv system is called a plumbing tree.

Double vanity drain pipe size. A single bathroom sink lavatory drain is 1 drain fixture unit. A double vanity can offer a his and hers sink. For example if two pipes are specified to be 10 inches apart you measure 10 inches between the centers of the pipes not 10 inches between the edges of the pipes. As with the term on center which is used for construction the term centerline is an imaginary vertical line drawn through a key reference point usually the drain pipe.

The current drain line in the crawl space is 1 1 2. I am replacing a single sink vanity with a double sink. Water runs down the sink drain into a p trap so called because it s shaped like the letter which fills up with water to prevent sewer gases and odors. I would like to use all 1 1 2 lines in the wall and connect to the 1 1 2 line to drain for both sinks.

Below our tables 1 and 2 summarize common plumbing code specifications for fixture venting and vent pipe sizes and distances that a plumbing fixture can be located horizontally from the vent stack. Minimum drain line size for a double bathroom sink vanity. Some older sinks may have drains that connect to a 1 1 4 inch tailpiece but most modern drains have a 1 1 2 inch outlet. The last size is 4 inch drain pipe that can be connected to 160 units in horizontal stack and 240 units in vertical stack.

Measure 21 inches approximately above the finished floor. The center of the lav s drain is located 18 approximately above the finished floor. Make sure you follow p3005 1 drainage fittings and connections and the reference table p3005 1 which specifies the proper pipe connections fittings to use to connect it all together. You ll see these distances also in our sketch at left.

Cut the tailpiece extending vertically down from each drain using a hacksaw so the pipe that extends from it can maintain a downward slope. The bathroom sink s water lines are roughed in 3 inches above the drain. Also notice the drain is centered right in the middle of this 30 inch vanity. Tables of plumbing drain pipe vent pipe sizes critical distances to plumbing fixtures.

Therefore a 1 1 2 inch drain will accommodate a double bathroom sink vanity. This line empties into a 3 line after about 10 feet and has a drop of over 6. This is the minimum size to use for building sewer or drain pipe that is connected to the toilet. All the pipes that connect to the tailpiece including the p trap assembly.