SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

Quoted from "TeaMan"

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.
TeaMan

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 www.irrigationtutorials.com, 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.

Quoted from "Fireguy97"

Quoted from "HooKooDooKu"

...

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.

...

Mick

Mick,

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.

Quoted from "HooKooDooKu"

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.



Mick

Thanks, that's good advice.

To protect the PVC above ground, you can paint it to help reduce the effects of UV light. But even better would be to transition from PVC underground to copper above ground. Obviously the copper is impervious to UV light, and you're unliking the crack the copper should you ever hit it with a weed-eater.

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.

The attatched image is a CRUDE drawing of how you could build feet. In the drawing, the small tubing at the ends represents the PVC. The larger tubing represents the copper, and the box represents the backflow device (RPZ or PVB).

HooKooDooKu has attached the following file:

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  Temp.jpg (17.83 kB - 3 times downloaded - Last download: May 4th 2013, 5:21pm)

I install RPZs outdoors, and they stay in place, even in sub-zero temperatures. Of course, all the water is removed from these devices prior to winter. Unfortunately, that removal requires partial disassembly of the RPZ. Follow mfr directions and you will be fine.

There are two models of RPZ that appear to be able to be winterized with a small (warm, but not hot, air temperature) compressor right through the device. One is the Watts 009, and I use those. The other is one I don't have experience with, and that is the Conbraco. What gives the Conbraco RPZ this appearance is the upward orientation of the check valves, and the lower-down location of one of the testcocks, needed to drain the lower portion of the device. (just the same, the first time I winterize one of those, I will still do the necessary disassembly to confirm that all the water is out)

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.
TeaMan

If the height of the heads and plumbing in the sprinkler system make a PVB an access problem, then you have to change to a RPZ device.

Thanks for the advice guys.
OK, makes sense to put it outdoors. I like the idea of unions to remove it. It will need to be mounted on the south west side of the house and will be in direct sunlight. I know PVC degrades in UV light. What do you recommend to use to get up to the device and back down to the manifold? I've heard of painting the PVC to ensure it handles UV light but am not sure what kind of paint bonds to PVC. I have to go pretty high on the house to get it above the highest head. Almost 4', this was another reason I was looking to put it indoors. Hide it in a sense rather than having it hanging on the side of the house. Point here is, it's more than a few inches of pipe to protect from UV light.
Any advice on this?

Just install the PVB outdoors and follow the manufacturer's care instructions as though your childrens' lives depended on it.