06-36 Backflow, head, clothes washer, laundry

Question: 06-36Code Section: 7Date:OBC 2006 Reference:,,,


1. In Is this not premise isolation? Why is the requirement for a check valve only and NOT a backflow preventer? (this is not a change but as I was reading it it looked like a change from before).

2. where did the 5′ head go?

3. Waste stacks serving more than one clothes washer may not be used to connect other waste pipes from other fixtures(i.e. basins or kitchen sinks) where pressure zones are created…. who will determine where pressure zones are created? Is this correct?

4. What difference does it make if the clothes washer connects to a laundry tray or not?


1. Provided both services are the same (potable or non-potable) a check valve is sufficient to prevent one service over-pressurizing the other.

2. In the 5 foot head was replaced with 3m. However, going through the roof would provide the highest pressure that the DWV plumbing system would see and the roof vent terminal would be acceptable.

3. Our best translation of this is – if a stack carries more than one clothes washer, tie separately into the building drain.

4. states a requirement for a minimum of 600 mm to prevent siphoning and/or backflow spillage to address the increased use of laundry boxes.