Venting a clothes washer drain line
Posted by Greg N on February 18, 2004 at 11:51:48:
An inspector pointed out that the drain line for our clothes washer is sloped improperly and has no vent and it should be corrected. The washer is about 14 feet from the main waste stack in our basement.
The current drain line for the washer is PVC (2" diameter?) that has a P trap and then runs 14 feet horizontally (with very little slope) and connects to the main drain line going out of the house.
I plan to install a new PVC drain line for the washer with the correct slope, but I'm unclear about the proper way to vent it.
1. Is it important where the vent I install on the drain line is located on the 14 ft run of PVC (from P trap by washer to the main stack)? It would be easier to locate the T for the drain line closer to the main stack because the existing vent lines are directly above the main stack in the upstairs bathroom.
I'm under the impression that the vent needs to be closer to the P trap (within 6 ft?) to be effective? Is this correct? If I need to put a vent within a short distance of the P trap, would it be valid to T into the waste line within a few feet of the P trap, run vertically up the ceiling in the basement, then turn and run horizontally for 10-12 feet, then turn and go vertically upstairs?

2. Adjacent to the main stack in the basement is an empty area where I hope to have a 2nd bathroom plumbed in the near future. What size PVC pipe should I use for a vent on the clothes washer line so I can tie into that in the future to vent fixtures in the 2nd bathroom (shower, sink, and toilet planned).
Since I have to cut through the floor above to run the vent for the clothes washer it seemed natural to plan for the future and make that run adequate to support future fixtures.

3. When I run the vent pipe up through the floor into the wall cavity of my upstairs bath, where should I elbow and connect into the upstairs vent? Should it be connected above the highest fixture (which would be the sink in the bathroom)?


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