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Advanced Member

Posts: 77

Location: Kamloops, In Beautiful British Columbia


Wednesday, September 14th 2011, 3:07am

All it takes is a PVC male and copper female and make place these joints under ground. You could even build "feet" into the copper pipe to support the backflow device without the risk of it getting knocked over and damaging the underground plumbing.

Plumbing code stipulates that every device or assembly be supported with proper supports. This doesn't mean supported by the pipe itself. A 1" RPZ is a heavy assembly. Pipe 'feet' is a hack install, and a major problem waiting to happen.

After everything is installed, don't forget to get it tested by an Authorized backflow assembly tester.

Irrigation Contractor

Certified Backflow Assembly Tester


Supreme Member


Wednesday, September 14th 2011, 12:06pm


Plumbing code stipulates that every device or assembly be supported with proper supports. This doesn't mean supported by the pipe itself. A 1" RPZ is a heavy assembly. Pipe 'feet' is a hack install, and a major problem waiting to happen.




If you're going to bother to chime in and knock my suggestion, do it properly!!! Don't just say my suggestion is wrong if you're not going to at least turn around and tell us what is right (i.e. just what is "proper supports").

After all, when I go to the Watts web site and look at their installation instructions for their Double Check Backflow Preventer, every picture simply shows the device supported by the plumbing pipes connected to the device. Nothing else. And while a back flow preventer IS a heavy device, a pair of 3/4" or 1" copper pipes are pretty #$%@ strong.


Supreme Member


Wednesday, September 14th 2011, 12:31pm

RE: RPZ devices

It appears that I need an RPZ device anyway. Glad I asked a few questions. I will have two supplies, one from a holding tank that collects rain water, and the other the municipal system. I need a device that will prevent backflow pressure as well as siphoning. Any recommendations on which to use. I don't want to break the bank, but want something familiar and easy to maintain. I saw three brands in Sprinkler Warehouse, Febco, Conbraco and Wilkins. It's a 1" main line coming from the meter and to the meter for all that's worth.
I did find something very interesting reading up on them in their installation instructions. For all three, they say not to install them outside in areas that freeze. They said freezing conditions will damage the devices. All say to install inside and pipe to a drain in areas that freeze. Now, I'm not sure what to do. I realize it will be winterized and drained, but it doesn't mention this. They seem pretty strict on it.

The manufacturer's instructions are for general use where the device is going to be used year round. An irrigation system is a "special" case because you should never be using the device while freezing conditions exist.

Just because you have a 1" main line does NOT mean you have to use a 1" RPZ. You might be able to use a cheaper 3/4" rather than a 1" by changing from a 1" pipe to 3/4" fittings just as the water enters/leaves the device (you should be able to either find a 1" solder to 3/4" threaded connection, or a 1" to 3/4" reducer coupling and a "street' female addapter that solders directly to the coupling).

In the case of the Watts 009, it looks like the 3/4" device is designed for flow rates upto around 40 gpm, with pressure losses <=15psi for flow rates below 24 gpm; while the 1" device is designed for flow rates upto around 80 gpm, with pressure losses <= 15psi for flow rates below 60 gpm. Given that a home owners is unlikely to be designing an irrigation system that uses much more than 20 gpm (and more likely to be designing for something like 12 gpm), the only reason to use a 1" Watts RPZ over a 3/4" Watts RPZ is for the convenience of not having to make the 1":3/4" transitions.

BTW, if you read, he says basically the same thing about valves... you might not always want to match the valve size to pipe size (after all, the internalls are MUCH smaller than the pipe size for any size). You need to instead look at the flow characteristics of the device and determine what is the right valve size based on your flow/pressure designs and not stricktly on pipe size.

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