Tuesday, May 21, 2013

How to Combine Toilet & Sink Drains

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How to Combine Toilet & Sink Drains


Bathrooms usually have more than one plumbing fixture, and it’s inconvenient and expensive to run individual drain lines from each fixture to the house’s main sewer line. Instead, plumbers connect drain lines in the floor beneath the bathroom and install a common vent that allows water and waste to drain without forming an airlock. The toilet has the largest drainpipe, so the sink drain, which is smaller in diameter, will empty into the toilet drain line.

The Toilet Drain

1-Connect a 3-inch PVC closet bend to the bottom of the toilet flange located in the floor where the toilet will sit. A closet bend is sweeping 90-degree elbow that connects the flange to a 3-inch drainpipe that runs between the floor joists. There is no need to install a trap beneath the toilet because toilets have built-in traps.
2-Attach the open end of the closet bend to a horizontal 3-inch drainpipe. The drainpipe runs horizontally only until it can descend to connect with the house’s main sewer line. The pipe is not perfectly horizontal; it should slope at the approximate rate of 1/4 inch per lineal foot. More slope is not necessarily better since liquid can outrun waste, leaving it stuck in the drainpipe.
3-Apply PVC prep liquid and PVC adhesive, as directed on each product’s label, when connecting PVC pipes and fittings that are not threaded.

The Sink Drain

1-Attach a 2-inch sink trap assembly to the bottom of the drain stub that extends from beneath the sink. This is a threaded connection, and the trap should come with two washers, one on each end that slip over the connecting pipes and tighten. Do not glue these connections.
2-Connect a horizontal PVC pipe to the bottom end of the trap assembly. This pipe should be long enough to reach the stud space in the wall behind the sink where it will attach to another 2-inch vertical pipe.
3-Install a 2-inch sanitary-T fitting in the stud space to connect the horizontal sink drainpipe to a vertical drainpipe. The vertical drainpipe serves two purposes; water drains downward, and the upper portion of the pipe ties into the house’s main vent stack. Without the upper vent portion of the pipe, water locks can form in the drain system. The sink vent serves both the sink and the toilet.
4-Run the lower sink drainpipe, adding elbows or collar connections as needed to reach the 3-inch drainpipe that runs from the toilet. The configuration depends upon your bathroom layout and the direction of the floor joists, but connect the sink drain to the toilet drain within 6 feet of the toilet, if possible.

The Connection

1-Connect the sink drainpipe to the toilet drainpipe using a 2-inch-to-3-inch sweeping-Y connector. The sink drain should enter the toilet drain from above, and the 2-inch opening for the sink drain should extend upward from the 3-inch horizontal drainpipe to prevent backflow issues.
2-Cut a section out of the 3-inch drainpipe when tying in the 2-inch sink drain and use the PVC prep liquid and PVC glue to hold the connections securely.
3-Cap the end of the 3-inch drainpipe before attaching it to the main sewer line, flush the toilet and fill the lines with water to test the pipe connections. This is the best time to discover if a connection leaks.

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