Standard Kitchen Sink Drain Pipe Size

The standard size and setting.

Standard kitchen sink drain pipe size.

When installing a new kitchen sink drain or repairing an old leaking one you need a particular size drainpipe. Sewer drains from laundry sinks or washing machines are 2 inches in diameter and those from sinks in the kitchen bathroom or powder room generally use a 1 5 inch pipe. Every state may have different code on plumbing and it may affect the required size of the bathroom sink pipe. The main sewer pipe leading to the septic tank or public sewer is usually 4 inches.

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 1 2 inch supply pipes that come to the sink each terminate with a shutoff valve and this valve is one of the two factors that determine the connector size on the faucet hose. All the pipes that connect to the tailpiece including the p trap assembly. This pipe is the standard size for all kitchen sinks.

The inlet must match the supply pipe and it can be a 1 2 inch female pipe thread fpt connector for galvanized pipes a 1 2 inch compression or sweat connector for. This size is precisely the diameter of the pipe instead of the length. A 2 inch sink strainer fits the standard bar sink drain. A standard rule of thumb is that sewer pipes leading away from a toilet are 3 inches in diameter.

These drains like bathroom and kitchen drains use a p trap which is a j shaped pipe that connects to the main drain line. However most of the bathroom sinks use 1 inch drain pipe.