Plumbing P Trap In Floor Joists

Erniecan tx i have this situation adding a bath upstairs in an old home.

Plumbing p trap in floor joists.

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. During the layout stage plan to run the drainpipes parallel to the floor joists when possible. The floor system is 2 10 joists spaced 12 inches on center. I am installing a shower in a first floor location that is cantilevered out from the house.

When you run your pipes through a joist you will have to be careful with your work. We cut out and doubled up a header where the tub p trap was to be installed. Install a sanitary tee facing into the room for the sink trap. That would result in an s trap which is prone to siphonage.

No room for 2nd floor tub trap. Prior to drilling holes in these floor joists we installed 3 4 inch plywood to each one. Install a piece of 1x6 blocking and anchor the pipe with a strap. The ideal height is usually 18 inches above the finished floor but check your sink instructions to be sure.

This gives the strength for the weight of tub and person and raises the floor enough to install a regular trap for the tub. Step 3 understand the joist slopes. Note the photos show a recent bathroom remodel where we relocated the tub drain across several floor joists. 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.

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. Cement a 1 1 4 inch trap adapter into the tee. The slope should be about 1 4 for each foot of pipe. Step 4 cut the holes.

The floor joists are 2 x 10s and the joist cavity is insulated.