Guides for owners, managers and supers

A cross-connection is any point where drinking water meets something that is not drinking water. What that means in a real building, how water flows the wrong way, and why the Region has a by-law.

Records released by the Region put real numbers on the Durham backflow program: about 4,800 devices on an annual schedule, 1 in 4 past due in August 2026, roughly 125 past-due letters a month.

A working checklist for the day the notice lands: read it, find the device, check the tag, book a registered tester, get the report filed, and set the reminder so next year is a formality.

BSI Online administers Durham's backflow program: notices, tester registration, report submission, the $25 fee. What an owner needs to know and what you do not need to do yourself.

The tag on a backflow preventer is required by Durham's by-law and carries specific fields. What each means, what a tag does not prove, and how it relates to the report and the Region's record.

The failure modes behind most failed tests: fouled checks, worn rubber, weak springs, stuck air inlets, weeping relief valves, freeze damage. Which devices get which, and what scale does.

Where the device usually is in a Durham commercial or multi-residential building, what it looks like, how to read the plate and tag, and how to tell a DCVA from an RPZ from a PVB.

When a Durham commercial building sells or a tenant changes, the backflow record, the annual test clock and the survey requirement move with it. What to ask for on closing and do first.