Help with Sprinkler Backflow Prevention

Can I use a continuous pressure double check valve when connecting my sprinkler system to my water line, such as this???
http://www.watts.com/pdf/ES-9DM3_M2.pdf
I've been recommended an Anti-siphon pressure vacuum breaker, such as:
http://www.watts.com/pdf/ES-800M4QT.pdf
But they are more expensive and much bigger.
There are no city codes in my area requiring the use of a backflow prevention device though I'd still like to put something in.
Andy
--
ashroyer

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ashroyer wrote:

Andy-
In all my spronkler vavle installtions I have used individual Champion anit-siphon valves rather than an input line anti-siphon device.
http://www.championirrigation.com/HTML_Pages/Cat_ASVs.html
brass on brass.............valves installed 20 years ago still working, some solenoids replaced
That said, I cannot see why the valve you propose would not work.
However examaning the pressure drop vs flow curves that you provided, I see that "your device" has a much larger pressure drop for a given flow
~15psi drop at 10gpm vs ~5psi for the "other type"
depends on your flow your system requires & how much pressure you can afford to lose.
cheers Bob
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ashroyer wrote:

Andy-
In all my spronkler vavle installtions I have used individual Champion anit-siphon valves rather than an input line anti-siphon device.
http://www.championirrigation.com/HTML_Pages/Cat_ASVs.html
brass on brass.............valves installed 20 years ago still working, some solenoids replaced
That said, I cannot see why the valve you propose would not work.
However examaning the pressure drop vs flow curves that you provided, I see that "your device" has a much larger pressure drop for a given flow
~15psi drop at 10gpm vs ~5psi for the "other type"
depends on your flow your system requires & how much pressure you can afford to lose.
cheers Bob
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The headings on the manufacturers pages clearly state that the double check valve is not intended for health hazard applications. I would consider water from the lawn being in my water lines a health hazard. I agree that it looks like the check valve would be better than nothing but is not the best reasonably available protection. I feel sure that codes require the siphon breaker and, despite many peoples opinions, have valid reasons for doing so. Codes are for protection against obvious and non-obvious hazards and compliance is always a good idea, whether there is enforcement or not. Kinda like stopping for traffic signals when no policeman is in sight
Just my opinion, others will disagree, and it's your decision. Don Young

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On Tue, 4 Apr 2006 18:35:24 +0100, ashroyer

Don't Anti-Siphon and Check Valves do different things?
If I understand it right, an anti-siphon valve allows air INTO your hose/pipe when it demands more water than you can supply, which keeps it from either (A) collapsing your hose/pipe or (B) Sucking water backwards out of other branches of your water system. Whereas a check-valve/backflow arrestor keeps water from running backwards in your hose/pipe when you get negative pressure.
It wouldn't hurt to have both.
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wrote:

You're right about the check valve being one way but an anti siphon valve simply prevents water from moving backwards when a vacuum develops in the supply line. (this should only happen if the main water supply were shut off and the sprinkler valve were still open). In this case, a flapper valve opens and lets air enter the supply pipe instead of siphoning water out of the sprinkler pipe itself.
A check valve is not perfect, some water may leak backward in a worn valve. Since water is in contact with both sides of the valve, bacteria can migrate upstream, this is the health concern. In the anti siphon valve, an air gap is created segregating the grey water from the supply.
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The purpose of a bfp device is to avoid contamination of the water supply. Forget codes. If there was a backflow just after you fertilize the lawn, your house is the first to be contaminated. Still want to save a few bucks?
If you can afford to put in a sprinkler system and have a fancy lawn, don't be a cheap prick when it comes to protecting your family. Use the right device.
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Edwin Pawlowski wrote:

I agree. Plus, when you go to sell the house, this is something that is likely to get flagged by a home inspector, even if local codes don't require it. For a lower price, it appears the ones he's looking at are brass. There are plastic versions available which are lower cost and what I would use.
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In my place, its buried, next to the meter, which only has the top inch or so exposed.
-- Email reply: please remove one letter from each side of "@" Spammers are Scammers. Exterminate them.
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