Anti-siphon device on outside faucets?

In California, my last two homes had those pesky anti-siphon adapters permanently mounted on each outdoor faucet. They are supposed to prevent water from flowing backward if the city water pressure were to suddenly drop. The backflow could supposedly lead to contamination of the water supply. These one way valves always leak and if you turn off the faucet while the garden hose is pressurized, the anti-siphon valve will discharge the pressure in the hose through some vent holes. This is when you will get a face full of water as the valve vents.

Do any of you know if these things are required per some state or local code? If I remove them, what is my liability? Do you inspect for these during home inspections? Is this just a California thing?

Thanks in advance for your feedback.
Greg Sullivan / Canyon Lake, CA.

Yes they are required in CA (CBC Chapter 6).

It’s just like any other code requirement. Once you’ve moved in, you can do what you want. When I inspect your home for a potential buyer, I will tell them that they are missing and recommend replacement.

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Hey Greg,

It is not just a California thing. They are everywhere. An anti-siphon device (or vacuum breaker) prevents unsanitary water from being pulled back through a garden hose and contaminating your water system. Otherwise known as a “Cross Connection”

I always look for them and report if they are present or not. I believe most building codes require them on homes built. But you would have to check with your local municipallity.

They are required where I inspect, at least by the city for sure, and I report them missing if so.

When I bought a house in Mt. Clemens, MI (Macomb County) I could not close on the house until the city inspector saw that they were installed. He also required a hand rail to the front porch before I could close. (1 step then step up onto the porch while holding the storm door open. He had me install the hand rail behind the storm door. I installed it while he watched. After he signed off on it he watched me remove it & put it in the trash. We all laughed. He said he would have done the same thing.)

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Mine do not vent water like that, they do make some strange noises at times while in use though.

I do not think that they are that concerned with your water system being contaminated, but it does get exciting when you contaminate the public water system.

Thanks for your feedback.

About one year ago, I tried to remove one of those anti-siphon valves from a back yard faucet. They are threaded onto the faucet and locked on with some type of pin that jams down on the threads. The pin will not let go of the faucet’s threads until it is drilled out. Of course, drilling it out ends up damaging the faucet’s threads. That forced me to replace the faucet with a new one.

If there’s an easier way to remove these anti-siphon valves - I haven’t found it - yet.

Thanks again,
Greg Sullivan / Canyon Lake, CA.

I thought they were put on with Superglue or Gorilla glue.

Usually that pin that you speak of is an allen headed set screw…and it is usually corroded all to shiite. I used to just turn the water off, hack the entire hose bibb off and solder a new one on.

As for them protecting their water…my Arizona Contractor’s License requires me to install PVB backflow protection on all the irrigation systems I install(ed).

The city’s stance was: YOU need to install this backflow prevention to help us guarantee the water we provide will not be contaminated, keeping the customers safe. LOL

Those hose bibb asv’s are useless anyway, most of them aren’t working right anymore…but they sure do look super!

Wanna know how we explained the need for cross connection to our clients that fought us on the price?



They used to ask me all the time, how the hell can water from the lawn area get sucked into my home, carrying with it all the pesticides/herbicides/fertilizers and dirt etc? How can it happen? Why do you need to charge me 300 dollars to install this thing that I didn’t have when the house was built? Why? How?

I would say here is one scenario:

Crack house down the street explodes…causing 2 or 3 other houses around it to explode causing a raging inferno requiring 15 fire trucks…they all tap into a hydrant, causing the water pressure and volume to all but disappear…the force of the fire engines pumps is so great that it literally sucks all the water OUT of the piping in your home…which creates a massive suction, thereby sucking the water out of your sprinkler system mainline, which then suckes the water out of 300 feet of lateral lines…of which the sprinkler heads are attached…the suction is so great that it sucks bits of dirt and fertilizer etc through those tiny holes in your drip emitters and the small orifices of you lawn heads…all the way back into the potable water system. When the water pressure comes back up after the fire is put out…the dirt/fert/herb/pest is in the system and will cause sickness disease and overall poor health.

As they stood there looking at me, dumfounded, trying to decide if I was full of it or just crazy or maybe even telling the truth…I would say : “Besides, if I don’t install it, I could lose my Contractor’s license!”

True Story

Thanks Tony. That gave me a good laugh.:slight_smile:




Nice, Brian. Thanks.

Now that I have stories, I can start calling out the lack of anti-siphon devices on those exterior faucets.

Most of these devices are easily replacable. They do go bad on occasion, especially if hose is left on in winter. The cheap ones usually available at the big box stores (bad places to shop for building materials in my opinion) are generally not replacable (have to replace the whole d*** thing.

Where should one shop, then?

I always shop at local yards. Get better service, actual knowledgable people, and (except for loss leaders) get better prices. When buying lumber, box stores generally have poorest quality and lousy selection.

What if one has no local yards?

There was a big story a few weeks ago about our last local yard closing up shop.

I’ve always stopped in at local yards but they just cannot match the prices at the big box stores, and I have never had any problem with quality. And I don’t think I’ve ever heard anyone before say that a box store had a lousy selection. In fact, that, and their low prices, are their biggest advantages. I’ve even found the employees to be very knowledgeable and helpful. Maybe it’s a Southern California thing specific to the box stores because no other industry here seems to be as helpful as the box stores.

My pleasure RR. Next time you see the termite truck, notice that not only do they have a backflow preventer but they are required to have an air gap when filling the pesticide tank with water (using the home owners hose bib).