Need to Understand Anti-Siphon vs AVB

Users who are viewing this thread

Todd F

New Member
Messages
8
Reaction score
0
Points
1
Location
North Carolina
Dear Forum,

I'm trying to understand if the "Anti-Siphon" function built into hose bibs today is effectively just an "Atmospheric Vacuum Breaker"?

Thanks so much,
...Todd
 

Reach4

Well-Known Member
Messages
38,749
Reaction score
4,400
Points
113
Location
IL
That is pretty much true. However I expect the anti-siphon valve on the hose bib to leak, and the vacuum breaker usually not to leak as readily. ;)
 

Todd F

New Member
Messages
8
Reaction score
0
Points
1
Location
North Carolina
That is pretty much true. However I expect the anti-siphon valve on the hose bib to leak, and the vacuum breaker usually not to leak as readily. ;)
I'm probably splitting hairs but...
Plumbing code SPECIFICALLY says you can't have a valve downstream of an "AVB"... but doesn't say "anti-siphon valve".
Just trying to see if I can make the case that AVB is NOT Anti-siphon?
Your thoughts?
Thanks ...Todd
 

Reach4

Well-Known Member
Messages
38,749
Reaction score
4,400
Points
113
Location
IL
That suggest a distinction: how about saying that an anti-siphon valve is a vacuum breaker that is after the last valve before a spigot intended to connect to a hose? That seems to go along with the way they are labeled when sold, right?

So I am suggesting that by putting a valve between the air admitance device and spigot, you cannot call that an anti-siphon valve servicing a hose spigot.

Clearly the vacuum breaker's job is to avoid a siphoning, but not to a hose. https://terrylove.com/forums/index....-for-softener-filter-on-input-or-output.63102 is a little thread discussing vacuum breakers for softeners. Water heaters not on the bottom floor should have a vacuum breaker.
 
Last edited:

Smooky

In the Trades
Messages
2,299
Reaction score
152
Points
63
Location
North Carolina
I'm probably splitting hairs but...
Plumbing code SPECIFICALLY says you can't have a valve downstream of an "AVB"... but doesn't say "anti-siphon valve".
Just trying to see if I can make the case that AVB is NOT Anti-siphon?
Your thoughts?
Thanks ...Todd


Sec. 70-578. - Definitions

Atmospheric vacuum breaker (AVB) means a device that prevents backsiphonage by creating an atmospheric vent when there is either negative pressure or subatmospheric pressure in a water system. It includes those devices permanently attached to a hose bibb ("hose bibb vacuum breaker").

https://www.municode.com/library/nc...nodeId=PTIICOOR_CH70UT_ARTVIICRNNCO_S70-578DE
 

hj

Master Plumber
Messages
33,599
Reaction score
1,037
Points
113
Location
Cave Creek, Arizona
Website
www.terrylove.com
A "backflow preventer" functions like a check valve whenever the downstream pressure is greater than the incoming pressure, which a "Vacuum breaker" would NOT detect or prevent.
 

Todd F

New Member
Messages
8
Reaction score
0
Points
1
Location
North Carolina
So in my situation where I want to attach a battery operated hose watering timer (see link below) to my hose bib and leave the water turned on so that it will irrigate while I'm sleeping - - 1) Can we agree with that the code says that I CANNOT DO THAT because the timer has an automatic shutoff valve that will be downstream of my hose bib anti-siphon valve
2) Is that because the anti-siphon is rendered effectively useless if its under continuous pressure/use?
3) And if that is true and my PRIMARY GOAL IS TO PREVENT BACKFLOW - - why can't I screw individual atmosphere vacuum breakers onto the 4 hose threads below the timer to protect each zone?

https://m.lowes.com/pd/Melnor-Digital-Timer/1000146765

Your Thoughts?

Thanks,
...Todd
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks