In addition to being extremely energy efficient, another key aspect of earthship sustainability is the ability these homes have to minimize water usage. This is particularly relevant in California where residents have suffered from drought conditions for several years. In this atmosphere of need the California legislature and local government have addressed the use of gray water on a statewide level, though in a conservative way that seems almost to hinder as much as to help.

As we reviewed the requirements for installing a septic system here in Butte Co., CA we ended up doing a little research into the requirements for gray water recycling. How gray water is dealt with can impact the design of a septic system and so we took the opportunity to dig into state regulations, as well as, those that govern our specific situation here.

From a state level Chapter 17 of the California plumbing code states:

Gray water taken from a house may be re-used for

“uses such as water closets (toilets), urinals, trap primer for floor drains and floor sinks, irrigation, industrial processes, water features, cooling tower makeup and other uses shall be approved by the Authority Having Jurisdiction (local planning commissions etc…).”

From: http://www.iapmo.org/2013%20California%20Plumbing%20Code/Chapter%2017.pdf

The Butte County Dept. of health says:

               Section 1612A.1 Indoor Use of Treated Graywater

Graywater shall not be allowed for indoor use, such as flushing toilets and urinals, unless treated by an on-site water treatment system approved by the Enforcing Agency. For the purposes of this section, graywater treated by an on-site water treatment system shall be considered “Treated Graywater”. Treated graywater and treated graywater systems shall comply with the provisions of this code except as otherwise provided in this chapter and all of the following.

• The treated graywater shall have a separate tank sized to minimize the length of time it is retained
• A maintenance and operation manual for the treatment system shall be kept at the location of the system.
• Treated graywater intended for use indoors shall meet the California Department of Public Health statewide uniform criteria for disinfected tertiary recycled water as provided in California Code of Regulations, Title 22 Section 60301.230.
• The treated graywater system shall be installed, inspected and tested as specified for reclaimed water systems in Sections 1618.0 and 1620.0 (these are other sections of the CA plumbing code).

From: http://www.buttecounty.net/Portals/21/Env_Health/Wastewater/GrayWaterInfo.pdf

The uniform criteria from the California Code of Regulations are:

               60301.230. Disinfected tertiary recycled water

“Disinfected tertiary recycled water” means a filtered and subsequently disinfected wastewater that meets the following criteria:

• The filtered wastewater has been disinfected by either:
• A chlorine disinfection process following filtration that provided a CT (the product of total chlorine residual and modal contact time measured at the same point) value of not less than 450 milligram-minutes per liter at all times with a modal contact time of at least 90 minutes, based on peak dry weather design flow; or
• A disinfection process that, when combined with the filtration process, has been demonstrated to inactivate and/or remove 99.999 percent of the plaque forming units of F-specific bacteriophage MS2, or polio virus in the wastewater. A virus that is at least as resistant to disinfection as polio virus may be use for purposes of the demonstration.
• The median concentration of total coliform bacteria measured in the disinfected effluent does not exceed MPN of 2.2 per 100 milliliters utilizing the bacteriological results of the last seven days for which analyses have been completed and the number of total coliform bacteria does not exceed an MPN of 233 per 100 milliliters in more than one sample in any 30 day period. No sample shall exceed an MPN of 240 total coliform bacteria per 100 milliliters.

From: http://www.cdph.ca.gov/certlic/drinkingwater/Documents/Recharge/Purplebookupdate6-01.PDF

Botanical Cells as a Filtration Process Within These Criteria

The point of the botanical cells is to biologically “clean” the gray water and prepare it for safe and efficient re-use. With this in mind it seems reasonable that the botanical cells designed into earthships meet the filtration requirement as specified in the California Code of Regulations. It may be necessary to combine this with another form of “disinfection” whether that is chlorine, or perhaps UV light exposure to meet the criteria laid out above.

Inquiries to several Earthship groups on Facebook led to some encouraging responses, particularly from the Canadian Earthships folks and the Gunter-Abbott Earthship build on Dry Creek, Kansas OK. Apparently testing has been performed on certain Canadian Earthships that may be helpful if we can track it down. If we can locate the data, we are hopeful that it would give us a jumping off point for our own graywater system, which we plan to design for CA standards. Interestingly, the Earthship Academy Students Facebook page was silent despite the fact that they have more followers on the page than any other. Perhaps our post was lost in the high volume of traffic over there or something, but I had expected them to the be the most  active in the discussion and have the most up to date information out of all the groups.

In any event, the answer to the original question:  Can Gray water be used in Butte Co., CA?, is yes. However, the requirements in this jurisdiction may be higher than those seen in others.

More updates to follow.