13-15 Backflow prevention and irrigation

Question: 13-21Code Section: 7Date: 8 October 2013OBC 2006 Reference:

Question Submitted: Regarding the proper placement of a backflow preventer for a lawn irrigation system. My landscaper installed a back flow preventer as shown “current”. He says the placement of a BFP outside is common. The fall blowout of the system protects it from freezing. The local City inspector (and manufacturer) says that “current” is acceptable but he prefers the BFP to be installed inside to better protect from freezing and backflow (if seasonal blowout is incorrectly done). Are both installations shown allowed? or widely accepted? Which way is best?

Interpretation: tells us that backflow preventers shall be selected, installed and tested in conformance with CAN/CSA-B64.10, “Manual for the Selection and Installation of Backflow Prevention Devices”
In that manual it states that a Dual Check valve (DuC) is only good for a minor hazard situation. An irrigation system is listed as a moderate to severe hazard (depending on the presence of chemical or not) requiring a testable device such as a Moderate Hazard Rated: Double Check Valve Assembly (DCVA), Pressure Vacuum Breaker (PVB) or a High Hazard Rated: Reduced Pressure Backflow Preventer (RP), once the intended use is confirmed.

As for the illustrations supplied for the installation:

The “Current Installation” would be permitted “with the proper device” as long as the device is correctly installed and adequately winterized to eliminate any possibilities of damage from freezing.

The “Alternate Installation” would not be permitted (as shown) as the hose bib cannot be installed on the protected irrigation line. Even if it was equipped with a hose end vacuum breaker, it is considered potable water at the bib and not part of the irrigation system. A hose bib for potable use could be relocated upstream of backflow preventer. For it to be acceptable a separate connection would have to be installed and mechanically plugged to facilitate blowing out the system for the winter.

The Code Tech Committee feels it is necessary to point out that a landscaper is not qualified (as required by Provincial regulations) to install backflow preventers. This is a job for a qualified plumber or properly supervised apprentice. The property owner should be made aware of this.