Waste water from the shower is known as "greywater" and is illegal to use for domestic purposes other than for a few specific uses in a limited number of municipalities.This is for obvious reasons around public health and safety.
Greywater from the shower contains organic materials like skin and hair, as well as soaps, detergents and anything else that people use in the bath and shower.In order for this water to be safely reused inside the house it would have to be filtered, treated (several different ways), and stored, which would be way more effort than the water saving would be worth.
In California, a new greywater regulation was passed last year by the Department of Housing and Community Development which allows for unpermitted simple greywater systems.
- This new regulation allows the installation of a single-source (shower) system that can be used in landscaping as long as you follow the HCD guidelines for installation.
- There is also a provision for more complex multi-source systems that must be permitted; you can see all of the information on California's new regulations here.
I would recommend that you research the current regulations in your state as well as your municipality. If you check with your local building department they can fill you in on current as well as future regulations regarding greywater.
- Your best bet for reusing shower greywater is to use it for watering your landscaping.
- Ideally shower water can be run by gravity to a fruit tree or planter. You can consult the 12-step California guidelines for simple, safe steps for such a system.
For more information:
Read Jesse Terzi's Q&A "We want to design a greywater system for the bathrooms we're renovating. Can you help?"