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New Member


Tuesday, September 3rd 2002, 8:30am

inline valves + backflow preventer or anti-siphon

I'm going to install an 8-zone sprinkler system . I think I may have two choices:

1. One backflow preventer + 8 inline valves
2. 8 anti-siphon valves

My questions:
For choice 1, what kind of backfow preventer should I need? Is this option is less expensive than second?


Supreme Member

Posts: 456

Location: USA


Tuesday, September 3rd 2002, 3:26pm

Option 2 will be cheaper, but I would install the 8 inlines with a backflow device. There is a link on the forum homepage on the bottom that lists all the kinds of backflows.


Active Member


Thursday, July 24th 2003, 4:08pm

You NEED a backflow prevention device. An anti-siphon control valve is NOT an acceptable substitute for a BFP device. The choice of devices is the subject of much controversy and widely varying local code requirements. Go to and read to your heart's content. Mr. Stryker makes pretty compelling arguments for the required use of such devices. I was a novice when I installed my system and I spent hours on his site. I followed all of his suggestions and my system turned out beautifully...the first time!


New Member

Posts: 3

Location: USA


Tuesday, August 19th 2003, 12:29pm

<b><font color="red">Their are several types of backflow devices made:</b></font id="red">

1. Air-Gap
2. Atmospheric (non-pressure) Type Vacuum Breaker
3. Pressure Vacuum Breaker {PVB}
4. Double Check Valve Assembly {DC}
5. Reduced Pressure Principle Assembly {RP}

<b><font color="red">When to use each:</b></font id="red">

1. Air Gap - Not Used For Sprinkler Systems: It is a physical separation of the supply pipe by at least two pipe diameters (never less than one inch) vertically above the overflow rim of the receiving vessel. In this case line pressure is lost. Therefore, a booster pump is usually needed downstream, unless the flow of the water by gravity is sufficient for the water use. With an air gap there is no direct connection between the supply main and the equipment.

2. Atmospheric Vacuum Breaker - should Not Be Used For Sprinkler Systems: Effective for both high- and low-hazard substances, but only protects against backsiphonage.

3. Pressure Vacuum Breaker - commonly used for Sprinkler Systems: Effective for both high- and low-hazard substances, but only manages backsiphonage.

4. Double Check Assembly - commonly used for Sprinkler Systems: Prevents backflow in backpressure or backsiphonage conditions, but is only effective for low-hazard substances, such as grass clippings, dirt or other aesthetically displeasing material.

5. Reduced Pressure Principle Assembly - Best Protection but not commonly used for Sprinkler Systems due to cost: Ideal for both backpressure and backsiphonage to prevent both high- and low-hazard substances from reaching the potable water supply.

<b><font color="red">Your situation:</b></font id="red">

Your local building code will typically state that you can use either:
Pressure Vacuum Breaker (PVB)
Double Check Valve Assembly (DCA)
or Reduced Pressure Principle type backflow prevention device.

They will not allow:
Atmospheric (non-pressure) Type Vacuum Breakers

You should use either the Pressure Vacuum Breaker Assembly or the double check valve assembly since they are a low cost but safe and common method of protecting your water supply and is on the approved list from your local building codes. The Reduced Pressure Principle Assembly {RP} is the most expensive but safest device and all local codes allow the use of this type of backflow device. However, for residential home use it is probably overkill unless you want the safest method possible.

<b><font color="red">Which size backflow device to use:</b></font id="red">

You should always match the backflow device size with the size mainline pipe you will be using to suply your sprinkler system. If you have a 1" mainline feeding yoursprinkler system, use a 1" backflow device.

<b><font color="red">Approved Equivalent:</font id="red"></b>

All Febco, Watts, and Conbraco types of backflow devices are equivalent approved devices when comparing type to type. You should have no problem using one brand or the other. They just want you to use a quality device recognized by the irrigation industry. You should be able to use any of these brands.

<b><font color="red">Use the link below for great easy to understand article on Backflow Devices:</b></font id="red">


Rays Sprinklers

Supreme Member

Posts: 493

Location: USA


Tuesday, August 19th 2003, 1:40pm

I would definatly use the inline valves with the one backflow preventor. For the inline valves i recommend that you use the Irritrol 2400T valve. I strongly recommend them for all systems. The backflow preventor you choose will determine location and installation methods....another advantage of youinstalling the inline valve (irritrol 2400T) is that you can bury the valves in the ground protected by the valve box, while antisiphon valves must be installled above ground 12" above the highest sprinkler head on the line. [8D]
Rays Above and Beyond Automatic Lawn Sprinklers


Supreme Member


Thursday, May 17th 2007, 4:55pm

i just realized this is an old post

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