Basement Bath Part 2 of 2

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Adding a bathroom to an unfinished basement creates a host of new opportunities for finishing the rest of the space. With a convenient bathroom, you can much more easily justify a downstairs recreation room, a wine cellar, a home theater, or additional bedrooms.

 

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Time to Complete:
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Continue to Step 1

Overview

Adding a bathroom to an unfinished basement creates a host of new opportunities for finishing the rest of the space. With a convenient bathroom, you can much more easily justify a downstairs recreation room, a wine cellar, a home theater, or additional bedrooms. Many new homes are pre-plumbed with available stub-outs for plumbing at the time the house is built. More likely, you’ll need to break up the concrete floor to install new drain and supply plumbing. This is exactly as much work as it sounds like, but with a jackhammer and some help, it is manageable.
Because horizontal plastic pipes cannot be encased in concrete, they must be laid in the granular fill beneath the concrete basement floor. Possible locations for the bathroom, therefore, are limited by how close the main sewer line is to the floor surface when it meets the main drain stack. Check local codes for other specific restrictions in your area.
Plan ahead for this project. Once you cut into the main waste-vent, there can be no drainage in the house until you have fully installed the new branch lines and sealed the joints. Make sure you have extra pipe and fittings on hand.
Sawing and jackhammering concrete (you’ll have to do this to run the new pipe line) produces large quantities of dust. Use plastic sheeting to block off other portions of the basement, and wear approved particulate dust masks.

From: The Complete Guide to Plumbing, 978-1-58923-378-2

What You'll Need

Tools:

Duct tape
Concrete or circular saw
Cold chisel
Hand maul
Plastic sheeting
Chalk line
Jackhammer
Work & rubber gloves
Eye & ear protection
Dust mask
Plastic bags
4-ft. level
Reciprocating saw
2 x 4 lumber
2 x 6 lumber
Duct tape
Riser clamps or plastic stack
TY combo
Primer
Solvent glue
Banded coupling
Rags
Concrete
Trowel
Fiberglass insulation
Power-actuated nailer

Materials:

Duct tape
Concrete or circular saw
Cold chisel
Hand maul
Plastic sheeting
Chalk line
Jackhammer
Work & rubber gloves
Eye & ear protection
Dust mask
Plastic bags
4-ft. level
Reciprocating saw
2 x 4 lumber
2 x 6 lumber
Duct tape
Riser clamps or plastic stack
TY combo
Primer
Solvent glue
Banded coupling
Rags
Concrete
Trowel
Fiberglass insulation
Power-actuated nailer

 

Step 1

How to Plumb a Basement Bath

Clean the outside of the old pipes thoroughly and apply primer. Also apply primer and solvent glue to the female surfaces of the union fittings in the assembly. Slide the fitting assembly over the primed ends of the drain stack and the drain line at the same time. This requires a little bit of play in one or both of the lines so you can manipulate the new assembly. If your existing pipes will not move at all, you’ll need to use a banded coupling on the drain stack to seal the gap.


Step 2

How to Plumb a Basement Bath

Cut and fit the components of the new drain line one piece at a time, starting at the stack. Use strings or boards to outline the wet wall, so vent placement is correct. Drain lines underground must be a minimum of 2". Use 3" x 2" reducing Ys to tie the shower drain line and the sink drain line into the toilet drain line. Install vertical drain and vent lines that are long enough to protrude well above the level of the finished floor.


Step 3

How to Plumb a Basement Bath

Check for leaks by pouring water into each new drain pipe. If the joints appear sound, contact your building department and arrange for your inspection (you must do this prior to covering the pipes). Plug the pipe openings with rags to prevent sewer gas from escaping. Note: Some local municipalities require an air test as well.


Step 4

How to Plumb a Basement Bath

Backfill around the pipes with the soil dug from the trench. Mix and pour new concrete to cover the trench, and trowel smooth. Allow the concrete to cure for 3 days. Some municipalities may require that isolation membrane be wrapped around vertical pipes where they will be surrounded by concrete—check with your local inspector.


Step 5

How to Plumb a Basement Bath

Build the wet wall from 2 x 6 lumber. The sill plate should be pressure treated, but the other members may be SPF. Notch the sill plate so the vent pipes clear it easily. Use masonry anchors or concrete nails and a powder-actuated nailer to attach the plate.


Step 6

How to Plumb a Basement Bath

Run 2" vent pipes through notches in the studs. Assemble with vent T and 90° fittings. The 2" pipes are larger than required, but using the same size as the drain lines eliminates the need for reducing fittings, and makes for less waste. The 90° fittings are typically less expensive than the vent elbows.


Step 7

How to Plumb a Basement Bath

Route the vent pipe to a point beneath a wall cavity running from the basement to the attic. Or, if there is another vent line closer that you can tie into (not very likely), go ahead and do that.


Step 8

How to Plumb a Basement Bath

Run vent pipe up through the floors above and either directly out through the roof or tie it to another vent pipe in the attic. Remove sections of wall surface as needed to bore holes for running the vent pipe through wall plates. Feed the vent pipe up into the wall cavity from the basement. Wedge the vent pipe in place while you solvent-glue the fittings. Support the vent pipe at each floor with plastic pipe hangers installed horizontally. Stuff fiberglass insulation into holes around pipes. Do not replace any wallcoverings until you have had your final inspection.


Step 9

How to Plumb a Basement Bath

Install the water supply plumbing. Compared to the drain-vent plumbing, this will seem remarkably easy.


 
 

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