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

Unless local codes require Anit-siphon valves, you just need to install a PVB, DC, or RPZ upstream of all the valves. Which one of these are allowed is also dependand upon local codes. Local codes will also dictact whether you can do the work yourself or if a certified plumber is required.

An RPZ will subtract 10-15 psi from your operating pressure. That's enough to affect performance. If elevation allows installation higher than any sprinkler head, then a Pressure Vacuum Breaker is a better choice. Cheaper, too.

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by JohnnyG101</i>
<br />I was told that all I needed was an RPZ. Can anyone make a reccomendation on which to get?
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An RPZ is what is considered the "strongest" of backflow options (i.e. most reliable at preventing backflow, almost no codes would ever prohibit its use). But as Wet_Boots points out, installing an RPZ could affect your systems performance because it's going to rob the system of 10-15psi operation pressure.

You might want to check with codes again and see if a lower-end backflow option is available. Again, as Wet_Boots points out, a PVB will steel less operating pressure from the system. I believe MOST building codes allow PVBs, but it has to be installed above the highest sprinkler head (RPZ only has to be installed above ground, relative position to rest of irrigation system doesn't mater).

The third option (and more likely to be disallowed by local codes than the PVB) is a DC (double check). Don't confuse this with a double check valve. A DC backflow preventer has test cocks with it so that after it has been installed, each check valve can be independently tested for proper operation. There is no way to verify that each check valve is working properly in a double check valve. A DC is considered the least safe option (and not recommended if anything is injected into the system such as a fertigation system). However it has the benefit that it can be installed just about anywhere. This would include a basement or underground in a meter box. An RPZ can't be installed in a basement (unless you have adequate drainage for the water that can spew from the device) and you can't install it underground (it can't be located such that the device becomes submerged should it start releasing water to prevent backflow).


<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by JohnnyG101</i>
<br />The height is no issue at all. Also, it doesnt look like the dude installed a drain valve either.

This is needed no? How else could I drain the main line before it hits any valves right?
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While installing the backflow, you can install a blowout port (AFTER the backflow preventer). The blowout port would allow you to connect an air compressor to the system and blow all the water out of the irrigation system (winterizing).

Shut the entire house off, and run the air through an existing hose bib.