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Backflow question


LawnSite Member
Ottawa, Ontario
Hey All,
I need some help. I've been doing alot of reading about back-flows. I guess it is very strict in the states. Here in Ontario I can't find any laws for installing back-flows, just that dual check valves "arn't code", and if the work is done by a contractor then a licensed plumber has to do the point of connection. All the companies around here just install dual check valves; but I read so many times that dual check valves are not for irrigation due to the fact that they can let toxins into the potable water source. My old boss, whose been in the industry for over 20 yrs (CIC CID CIT certifications) installs 3 systems a day on average. All of which are installed with dual check valves.
Could it be that he has not read what I have?
I'm planning on doing some of my own installs this year and I want to install proper back-flows. I have recently purchased a couple of Pressure Vacuum Back-flows and one double check back-flow.
I was wondering, how well can PVB's withstand freezing temperatures?
If the system is blown out correctly, is it safe to leave the PVB outside in the winter?

Mad Estonian

LawnSite Senior Member
Vancouver Island
The regulation side of things depends on how seriously your local water purveyor is taking the backflow issue. For the Victoria area here, the purveyor is starting to mandate DCVAs on all new irrigation installs, with annual testing of all assemblies. Dual checks may not be to code in your area, but if there's no enforcement, not many contractors are going to be pushing a couple hundred extra bucks on their customers. Seems a lot of people on the site here live in areas where RPBAs are mandated, they decided that wouldn't be practical here (there's lots of threads you can look up on here with arguments for and against the various assemblies). As far as the PVB goes, I don't think there's any problem with leaving it out for the winter, but we were taught not to blow out systems with PVBs or AVBs because you're not supposed to apply backpressure to them (and you can't have your blowout upstream of course, that's a cross connection). So they need to be drained with a low point drain instead. I don't know, I've never dealt with one outside of the work shop. I'm sure others can enlighten us further.
So now the Sens are Canada's only hope...


LawnSite Silver Member
S.E. Michigan
PVB's are what I mostly deal with. Properly winterized, they hold up very well in the winter. All of them are outdoors.