Basement Bath Part 1 of 2

Return to Step by Step Listings

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.

 

Difficulty Level:
Time to Complete:
Estimated Cost:
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

Basement Bathroom Features

Our demonstration bathroom includes a shower, toilet, and pedestal sink arranged in a line to simplify trenching. A 2" drain pipe services the new shower and sink; a 3" pipe services the new toilet. The drain pipes converge at a Y-fitting joined to the existing main drain. The toilet and sink have individual vent pipes that meet inside the wet wall before extending up into the attic, where they join the main waste-vent stack.


Step 2

How to Plumb a Basement Bath

Mark the proposed location of the basement bathroom on the basement floor, using tape. Include the walls, wet wall, and fixture locations. The easiest configuration is to install all the fixtures against the wet wall, which will contain the water supply and vents. The drain lines should run parallel to the wet wall in the most direct route to the main waste-vent stack. Mark the drain line location (typically around 6" out from the wet wall).


Step 3

How to Plumb a Basement Bath

Cut out the area around the main stack. Use a concrete saw or a circular saw with a masonry blade to score a 24" x 24" square cutting line around the waste-vent stack. The cut should be at least 1" deep.


Step 4

How to Plumb a Basement Bath

Remove concrete and dirt around the main stack. Using a cold chisel and hand maul, strike along the scored cutting lines to chip out the concrete around the main soil stack. If necessary, break up the concrete within the square so it can be removed. Take care not to damage the pipe. Excavate within the square to determine the depth of the sewer line where it meets the main stack. Tip: Calculate the distance you want the new branch drain to run and multiply by 1⁄4". Add the thickness of concrete floor to this number to find the minimum depth the sewer line must be to accommodate your layout plan. If you excavate an inch or two past this depth, there is no need to dig farther.


Step 5

How to Plumb a Basement Bath

Excavate the drainline trench. Enclose the work area with plastic sheeting to protect the rest of the house from concrete dust. Use a chalk line to lay out a 24"-wide trench centered over the new branch drain location. Score along the lines with a concrete saw or a circular saw with a masonry blade.


Step 6

How to Plumb a Basement Bath

Use a jackhammer to break up the concrete in the trench, taking care not to damage any of the existing plumbing lines. Wear gloves, eye and ear protection, and a dust mask. Remove the concrete for disposal. Remove dirt (technically called granular fill) in the trench, starting at the main waste-vent stack.


Step 7

How to Plumb a Basement Bath

Create a flat-bottomed trench that slopes toward the main stack at 1⁄4" per foot. The soil will hold up the drain lines, so it is important to create an even surface. Use a hand tamper to tamp down the soil if it has been disturbed. Tape a 1" spacer to the end of a 4-ft. level to create a handy measuring tool for checking the proper slope. Set the soil aside to use for back fill.


Step 8

How to Plumb a Basement Bath

Cut the drain line or main stack (depending on how deep the drain line is) using a reciprocating saw (or a snap cutter). Support the main waste-vent stack before cutting. Use a 2 x 4 and duct tape for a plastic stack, or riser clamps for a cast iron stack. If cutting the horizontal drain line, cut as close as possible to the stack.


Step 9

How to Plumb a Basement Bath

Cut into the stack above the cleanout, and remove the pipe and fittings. Wear rubber gloves, and have a large plastic bag and rags ready, as old pipes and fittings may be coated with sewer sludge. Remember that no waste water can flow in the house while the pipes are cut open. Turn off the water and drain toilets to prevent accidental use.


Step 10

How to Plumb a Basement Bath

Cut and test-fit a new cleanout and long sweep TY combo assembly, dry-fitting it to the drain stack and the horizontal drain line to the street. Make any needed adjustments and then solvent-glue the fittings and new pipe into a single assembly.


 
 

Comments

Before you can comment, please Sign Up or Log In

© Copyright 2014, BLACK+DECKER Inc. All rights reserved. "BLACK & DECKER","BLACK+DECKER", and the BLACK & DECKER and BLACK+DECKER logos and product names are either registered trade marks or trade marks of "The Black & Decker Corporation"

Forgot Password?

x