Gray Water Use in New York

Being a New York green contractor involves pushing two very important elements through DOB code approval:
1. composting toilets
2. gray water and rain water for flushing toilets.

We recently tried to get composting toilets approved for our Passive House in Harlem but it got shot down. We will persevere trying to get it legalized in NYC but for now it can’t be done legally.

Here is the latest on DOB code regarding gray water, as discused between myself, Joe Schaffer PE, and Victoria Ann Vele, Social Media and Water Research Intern and Benjamin Cole, Legal Intern, both for Living City Brooklyn Gowanus, Living City Block.


Victoria to Ben: Can you help me find NY laws and regulations for grey water use in residences? I think its illegal.

Ben to Victoria:  Here is what I found, below. The highlighted portion seems to answer your question, but it’s worded strangely.  (Does it mean lavatory gray water can only be recycled from commercial office buildings or does it mean all gray water must be lavatory gray water from commercial office buildings?

From the NYC Construction Codes:

§ PC C101: Water Recycling Systems

C101.1  General. Water recycling systems shall receive storm water captured from roofs and balconies, condensate reclamation systems, gray water discharge only of lavatories from public restrooms in commercial office buildings, and the treated effluent from an approved black water treatment system as regulated by Department of Health and Mental Hygiene. Recycled water shall be utilized only for flushing water closets and urinals, cooling tower makeup and irrigation systems that are located in the same lot as the water recycling system. Recycled water shall be considered non-potable. Such systems shall comply with sections C101.2 through C101.12.

C101.2  Definitions. The following terms shall have the meanings shown herein.

BLACK WATER. Waste water discharged from water closets, urinals and any other fixtures discharging animal or vegetable matter in suspension or solution.

GRAY WATER. Waste water discharged from lavatories, bathtubs, showers, clothes washers and laundry sinks.

C101.3  Installation. All drain, waste and vent piping associated with gray or black water recycling systems shall be installed in full compliance with this code.

C101.4  Reservoir. Water captured for recycling purposes shall be collected in an approved reservoir constructed of durable, nonabsorbent and corrosion-resistant materials. The reservoir shall be a closed and gas-tight vessel. Access openings shall be provided to allow inspection and cleaning of the reservoir interior. The holding capacity of the reservoir shall be a minimum of twice the volume of water required to meet the daily flushing requirements of the fixtures supplied with recycled water, but not less than 50 gallons (189 L).

C101.5  Filtration. All water entering the reservoir shall pass through an approved filter such as a media, sand or diatomaceous earth filter. Filter may be installed in a sidestream arrangement sized to filter the entire volume of the tank at a rate equal to four times the recycled water in a one-hour period.

C101.6  Disinfection. Recycled water shall be disinfected by an approved method that employs ultraviolet or one or more disinfectants such as chlorine, iodine or ozone.

C101.7  Makeup water. Potable water shall be supplied as a source of makeup water for the recycled water system. The potable water supply shall be protected against backflow in accordance with Section PC 608. There shall be a full-open valve on the makeup water supply line to the reservoir.

C101.8  Overflow. The collection reservoir shall be equipped with an overflow pipe of the same diameter as the influent pipe for the captured water. The overflow shall be directly connected to the building house drainage system.

C101.9  Drain. A drain shall be located at the lowest point of the collection reservoir and shall be directly connected to the sanitary drainage system. The drain shall be a minimum of 4 inch (102 mm) diameter and shall be provided with a full-open valve.

C101.10  Vent required. The reservoir shall be provided with a vent sized in accordance with Chapter 9 based on the size of the reservoir influent pipe.

C101.11  Coloring. The recycled water shall be dyed blue or green with a food grade vegetable dye before such water is supplied to the fixtures.

C101.12  Identification. All recycled water distribution piping and reservoirs shall be identified as containing nonpotable water. Piping identification shall be in accordance with Section 608.8.

Victoria to Gennaro Brooks-Church: Does the highlighted portion mean that you can use grey water in toilets in commercial buildings only?

Gennaro Brooks-Church to Joe: Can you help me make sense of the gray water code? I says it is ok for commercial but not residential? And there is no mention of testing?

Joe: You’ll note that the system is required to use “approved” devices for filtration, disinfection, and dye injection.  This approval would come from DOB’s Office of Technical Certification and Research (OTCR).  OTCR recently released a technical bulletin covering water recycling and reclamation systems. This technical bulletin has the force of an interim code update; a full update is due out soon and will reflect the testing requirements noted therein.

The practical upshot of the technical bulletin is that a manufactured lavatory to toilet device (such as a Sloan Aqus unit), irrigation, and cooling tower make-up is allowed without testing, but any other in-building use requires a testing regime.  My interpretation is that this bulletin applies to any use (commercial, residential, industrial).


So…what does this all mean? My interpretation is that gray water through lack of any clear DOB documentation wasn’t illegal for flushing toilets. It basically flew under the radar. But now with the advent of OTCR attempting to regulate NYC gray water, which is a good thing, they have made it illegal or completely cost prohibitive, which is a bad thing. At least for the time being until the OTCR realizes your toilet is always going to be dirtier than any gray or rain water and the testing is silly.

Think about it, a toilet is a dirty place. Why do we have to have such strict water cleanliness levels to flush it? If a child plays in the toilet water, whether it be fresh city water, gray water, or rain water, you are going to have a problem. It is pretty irrelevant what the water source is (within the limits of gray/rain water) because once it hits the bowl it becomes contaminated anyway.

With this new regulation for testing you can’t just set up a functional gray water system (or rain water system) that feeds toilets in a Brooklyn brownstone. That is illegal now. You need go through the rigorous water testing process as outlined by the OTCR. At about $10,000 per year, the costs involved are too expensive for a residence. The testing may make sense for a large institution like a university, but only with the hope of showing the DOB that the water is clean enough and that testing is not necessary.

There are two things at play here. One is the early adopter home owner who understands the risks and benefits of gray water and chooses to install it without DOB approval and without testing. It is illegal but it is more ecological than the current arrangement of flushing with potable water (crazy!) and it does increase social acceptance of an important thing. I call it civil disobedience.

The second thing is large scale implementation of gray water. This is where it is very important that the DOB be on top of things. If gray water became widely used in NYC without DOB control you would have problems. Early adopter home owners is one thing but uneducated tenants in a large apartment building is a whole different thing. And that is the level the OTCR has to think. I call it the lowest common denominator.

So until DOB sorts things out and finds a working solution for gray water use in NYC, green building companies like Eco Brooklyn will just have to wait.

What is legal is rain water capture and gray water use for the garden. The basic concept is that water can leave the house but it can’t be used within the house. So you can’t capture rain water and bring it into the house for flushing toilets or showers. Likewise you are allowed to collect the house gray water and pass it to the green roof and garden. That is legal and a great second option to the flushing toilets with it.

It is perfectly legal to run the plumbing lines now, either for passing gray water to the garden or in anticipation for using gray water on toilets. To do this you simply seperate the kitchen sink and toilet drains (black water) from the bathroom sink, shower, tub and laundry drains (gray water).

The two seperate drains go to the basement where you combine them again and dump them both into the mains sewer. This prepares the plumbing for the gray water tank. Later when the DOB allows it you seperate the gray water drain and pass it into the gray water tank. You hook the tank to the toilet water line (that was also plumbed seperately from the other water line) and you have a functional gray water system.

Of course there is a lot more to it in terms of keeping the gray water from going putrid but that is the basic setup.

Hopefully it will be sorted out sooner than later. Eco Brooklyn is actively working with the DOB, if you can call it that, to increase their awareness of composting toilets and gray/rain water, even if it simply means we apply for the system and they reject it. At least they know it exists and people want to do it.


3 thoughts on “Gray Water Use in New York

  1. Hi, you mention that greywater for irrigation is legal in NY, but I don’t see that codes are included in the onsite wastewater treatment regulations. They only mention separate greywater septic tanks. Do you know where I can find the regulations that specify legality of greywater irrigation systems?

  2. Thank you for posting this very important issue/topic. I am truly enthused by your motivation. I think we as “green” contractors need to factor the basic economics of green technologies. NYC sells water to property owners, if the “owners” use less water, NYC makes less money. Simple economics! When, not if, NYC government allows grey water for toilet use, we will see a reflected increase in the costs associated with water consumption. The rich stay rich!

  3. Thanks for posting your findings and interpretations on greywater use in NYC.
    It looks like what you want to do is to flush toilets with used lavatory water, primarily. That makes a lot of sense, and as we know, is done elsewhere.

    I am trying to be able to use harvested rainwater to flush toilets. Green roofs are often appealing to condo owners who do not have access to a backyard. If their surplus rainwater can be used to flush toilets, it would be a great boon to the local environment. The system could be put in place when the green roof work is done.

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