Parent Category: Code Tech Database
Category: Cross-connections

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Question: 13-17 Code Section: 7 Date: 2 October 2013 OBC 2006 Reference:

 Question Submitted: We are in the process of removing a grey water system with a chlorinator in a single family dwelling. The non-potable piping must now be reconnected to potable to serve the toilets. The system used an air gap on the make-up water. Is a Dual Check with Atmospheric Port (i.e. Apollo 404, Watts 9D) an acceptable form of backflow protection between the potable and non-potable systems until a new system can be installed?

Interpretation: The proposed potable water supply connection will not be acceptable based on the following regulation: Connection of Systems
(1) Connections to potable water systems shall be designed and installed so that nonpotable water or substances that may render the water non-potable cannot enter the system. Protection from Backflow
(1) Except as provided in Sentence (3) and Articles To, where a backflow preventer is required by this Subsection, the backflow preventer shall be selected, installed and tested in conformance with CSA B64.10, “Selection and Installation of Backflow Preventers”. Non-Potable Connection
(2) Make-up water may be supplied to the non-potable water system by,
(a) a reduced pressure backflow preventer, or
(b) An air gap.
When there is a proposal to supply potable water with a connection being made to connect to an existing non-potable system (i.e. including the re-use of storm sewage or greywater design system), either an RP selected in accordance with the CSA B64.10 Standard, or air gap conforming to the Building Code must be used. Storm sewage or greywater that is free of solids may be used for the flushing of
(a) water closets,
(b) urinals
(c) sub-surface irrigation, or
(d) the priming of traps. Greywater means sanitary sewage of domestic origin that is derived from fixtures other than
sanitary units.

The committee agrees that the greywater system is deemed to be a high hazard type non-potable water system which will require an RP backflow prevention device to be installed at the connection between the potable water supply and the non-potable supply piping to the toilet. The Dual Check with Atmospheric Port according to the CAN/CSA B64.1 manual is only rated for “minor hazards”. With the elimination of the proper “air gap”, this installation would require a high hazard device as approved in the B64.1, such as, a Reduced Pressure Principal backflow preventer (RP).