In the City of Austin, you are required to obtain an auxiliary water permit if you are installing a graywater reuse system. There are two types of permits for graywater reuse systems. One is a Homestead Permit which allows a homeowner to install a gravity based graywater reuse system that drains from your clothes washer. This is called a “laundry-to-landscape” system.
If you want to connect multiple graywater fixtures (shower/bath tub, bath sink, clothes washer) to a gravity based graywater reuse system or if you want to install a pressurized graywater system, then you will need to obtain an auxiliary water permit and the services of a professional engineer or master plumber to design and install your system.
In addition, by installing a pressurized graywater system, you will be required to install a special backflow prevention device called a Reduced Pressure Zone (RPZ) backflow prevention device at your water meter.
But now you may be asking, “I won’t be connecting my pressurized graywater system to any municipal water pipes. Why do I still need to install this RPZ backflow prevention device?”. The simple answer is that your pressurized graywater reuse system has the “potential” to push graywater back into the municipal water grid due the presence of the pump if a pressurized graywater pipe somehow becomes connected to your house’s plumbing system. The pump can produce higher pressures than the municipal water pressure at your house, therefore pushing graywater into the municipal water grid.
If you are not in the City of Austin, you definitely want to check with your municipality as they may have different permit requirements.