Expert advice for planning a plumbing remodel. Includes diagrams of where toilets and sinks should be placed, as well as tips on routing supply lines and drain pipes.  New fixtures can be installed above or below the soil stack.

Planning any plumbing addition requires that you think about code restrictions, the limitations of your system’s layout, and your own capabilities.

It’s not hard to run supply lines to a new place, but it is a challenge to tie into drain-waste vent (DWV) pipes. Connecting a fixture to an existing soil stack is the simplest and most cost-effective way to add it. It is common to place them piggyback style above or below existing fixtures, as shown in the right. However, codes may restrict their use.

In addition, you can also place the fixture(s) back-to-back with the existing group attached at the soil stack. If you plan to add a room across your house from existing plumbing, you will need to run a vent stack through the roof. A new branch drain must be connected to the soil stack (see the below right), or via an existing clean-out to the main house drain.

If possible, tie a bathroom sink or tub directly into an existing branch drainage to save labor costs. After you have figured out a way to tie into your DWV system the next step is to research possible access routes to run pipes to new appliances or fixtures. First and foremost, you need to know the basics of house anatomy.

There are three notable ways to install new fixtures: above or below the soil stack (A), backwards with existing installations (B), with a new vent stack (C) and with a branch drain (C).