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Active Member

Posts: 6

Location: USA


Tuesday, August 19th 2003, 4:16am

Local Code Lingo

Can anyone help? I plan on installing a sprinkler system myself. I started by looking up my local building codes. Everything was clear to me EXCEPT one part on the backflow prevention. I will write exactly what the code states and maybe someone can help me out.

There are 2 approved types of backflow prevention devices.

1. Air-gap separation to be approved shall be twice the diameter of the supply pipe, measured vertically above the rim of the vessel, but in no case less than (3) inches.

2. Double-check valve assemblies or reduced pressure principle backflow prevention devices shall be of Watts manufacture series No. 709 or 909 or an approved equivalent.

My main question is on number 1. Are they talking about a pressure vacuum breaker? What size would I need if I am using a 1 inch supply line in order to keep with the "twice the diameter" statement?

On number 2, is the Febco double check an equivalent to the Watts series No. 709 or 909?

Any help?


New Member

Posts: 3

Location: USA


Tuesday, August 19th 2003, 12:11pm


<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 states above that you can use either:
Double Check Valve Assembly
or Reduced Pressure Principle type backflow prevention device.

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

You should use the double check valve assembly since is it 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 suuply 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">



Active Member

Posts: 6

Location: USA


Tuesday, August 19th 2003, 1:44pm


That answered all of my questions!

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