Plumbing P Trap In Floor Joists

Install a sanitary tee facing into the room for the sink trap.

Plumbing p trap in floor joists. Cement a 1 1 4 inch trap adapter into the tee. No room for 2nd floor tub trap. Problem is the p trap almost touches the bottom of the joist cavity and is likely to freeze being very close to the exterior of the house. This gives the strength for the weight of tub and person and raises the floor enough to install a regular trap for the tub.

The floor joists are 2 x 10s and the joist cavity is insulated. You need to raise not only the trap but also the connection to the vent such that there s a maximum pitch of 1 4 per foot along the entire waste pipe between the trap and its vent. We cut out and doubled up a header where the tub p trap was to be installed. This would mean drilling the joists and re routing the entire run.

Step 3 understand the joist slopes. An important step in running drain lines occurs on paper before the actual plumbing begins. Erniecan tx i have this situation adding a bath upstairs in an old home. Note the photos show a recent bathroom remodel where we relocated the tub drain across several floor joists.

During the layout stage plan to run the drainpipes parallel to the floor joists when possible. I will accomplish two things by installing 2x8 joists where the tub is going. The holes will have to follow a straight line that goes across the floor and has to either go up or go down so the pipe has a slope. The slope should be about 1 4 for each foot of pipe.

Step 4 cut the holes. Install a piece of 1x6 blocking and anchor the pipe with a strap. That would result in an s trap which is prone to siphonage. When you run your pipes through a joist you will have to be careful with your work.

The ideal height is usually 18 inches above the finished floor but check your sink instructions to be sure.