A remodel or expansion presents the single best opportunity to retrofit your home with graywater plumbing. Work is already being done, wiring is often accessible, optimally even the floor is removed. This is the time you have easy access.
Even if you don’t have immediate graywater plans, it makes sense to jump on the chance and put in the plumbing now. If you need to leave things unfinished, it’s totally fine, you can simply stub out the pipes. You’ll thank yourself many times over later on. It might even increase the sale value of your home.
Here is a video showing how to install graywater plumbing for sinks and bath/shower under the floor of a house during a remodel. You’ll see the fittings involved, special tools called for in this case, and the routing of pipes for various options:
- Graywater out to a surge tank for use in the garden
- Graywater diverted to the sewer
- Graywater overflow from the surge tank back into the sewer when necessary
You can see that this kind of work is much more complicated than laundry to landscape. Because it alters the existing plumbing and ties into the municipal system, it requires a permit.
As involved as it is, it still follows the same core principles of any graywater system as laid out on our Build page:
- Use of a 3-way diverter valve
- Sloping the pipes 2% (1/4 inch of drop for each foot of run)
- Not storing graywater for more than 24 hours (in this case planning for a surge tank)
- Sending the graywater to mulch basins in the garden where it will be released below the surface (this part not shown in the video)
Upstairs Graywater Plumbing Challenge
Plumbing for graywater during a renovation also presents the unique opportunity to easily include water from upstairs sinks, showers, tubs and laundry machines. Retrofitting second floor (or higher) fixtures can be problematic in normal times because the drain pipes merge with the toilet’s blackwater line almost immediately, before descending under the house where you usually get at them.
With construction underway and the walls and floors opened up, new graywater pipes can be installed with ease, running parallel to the blackwater line. Imagine having to insert a new pipe through the inside of a wall from upstairs to below the ground floor, through the insulation, the wiring, the crossbeams – it would be just about impossible.
Backflow Preventer
One important addition here is a backflow preventer. As you see at 11:35 in the video above, if the sewer ever blocks up, the backflow preventer keeps the sewage from running back up the pipes and into the surge tank or into the sink and bath drains inside the house. When you connect your graywater plumbing to the municipal system, you need this kind of isolation cutoff.
Professional Installers
In this case, the installers are a professional company hired for the job. But if you study the video closely, you may decide you can do it yourself after all. The core principles are always the same.
However, it may be a matter of legality – see our Legal page, and check with your local jurisdiction, whether it’s the city, county or state. Bring your carefully thought-out plan when you apply for your permit, and ask about special situations, like the need to core-drill through the foundation as in this video. That might be something that requires a contractor’s license where you are. You don’t want to accidentally compromise the structural integrity of your house.