View Full Version : Sprinkler Air Vacuum breaker vs Pressure vacuum breaker

Mike Pascutiu
05-24-2005, 08:59 AM
I was requested by the City watter system to change my Sprinkler Air Vacuum breaker with Pressure vacuum breaker.

Why would the last perform better than the air vacuum breakers? The City clerk was not able to explain me the reason of the request?

This change would cost me close to 100$ plus the time to do it.

Would replacing the regular sprinkler valves with ones that have Antishiphon valves do the same result as changing over to Pressure Vacuum breaker valves?

Thank you,


05-24-2005, 10:31 AM
The atmospheric vacuum breaker/backflow preventers are not designed to have pressure on the downstream side of them. Your system has the valves after the VB so it always has pressure on it. The poppet floats on the water during periods of flow and drops down when the flow stops. Having continual pressure can bond the poppet to the seat, and since it is not spring loaded it probably would not drop down to open the vent in a backflow condition. The valves with vacuum breakers do comply with the requirement, as long as the valves are installed at least 12" higher than the highest sprinkler head and at least 12" above the ground. Unless you only have a few zones, installing a central pressure vacuum breaker will probably be less expensive than all new valves and the piping to accomodate them.

Mike Pascutiu
05-24-2005, 10:53 AM
Thanks for the details. It makes more sense now, and I will change over the sprinkler valves to the one with antishyphon one.

Oddly enough, I have two sprinkler lines running out of the house, so I would need two Pressure Vacuum breaker valves, 160$ !!

Thanks again,


05-24-2005, 07:21 PM
Usually installing the other valves the way they are required to be creates an "unsightly" appearance.

05-24-2005, 10:06 PM
While the Community Official was correct, and the replies you have received were also correct and factual, it still does not excuse the poor training that your tax dollars obviously go into. If a community requires something, they should be able to tell you why. They should be able to either explain the reasoning or put you in touch with someone who can. Just enforcing a requirement with no reason as to why they are enforcing it is unacceptable. Unfortunately that is the d******* way of thinking. Big government rules and the citizen should just comply without question.

05-25-2005, 05:54 AM
The city clerk is basically a secretary. Does your secretary know all the technical details about your company? NO! And the city clerk does not know the building codes, even some inspectors don't. There could be many reasons for not getting an answer, such as, the inspectors were still out in the field, the inspection department might be in a different location, or the customer did not insist on an answer and the clerk thought it was just an academic question. Aat least she/he did not try to make up an answer like Home Depot clerks would.

05-25-2005, 08:35 PM
[QUOTEI was requested by the City watter system

Was that actually a "request" or was it a " change by .....date.... or it will be $250 per day fine"?

05-25-2005, 09:15 PM
Hence my quantifying statement that whomever is making the request of the homeowner be prepared to point them in the proper direction so that the questions or concerns are addressed. Many ordinances are easy to quantify and explain, such as keeping one's grass cut, but some are more technical, and if I didn't know why I was being asked to do something, I would hope that someone would be avaliable to answer questions.

That's all, I didn't want to come across the wrong way.

Gary Swart
05-25-2005, 11:46 PM
I find it hard to believe that no one explained that a backflow preventing valve is necessary to prevent possible contamination of your domestic water. I don't know how your city operates, but mine has a handout with all of the information one needs to get the right type of equipment. It explains where to get it, how to install it, and what it is for. It's not a big secret, nor is it hard to understand. In my city, the city water department makes the first inspection after the installation, then we get an annual reminder to contact an authorized subcontractor to perform a test to verify that everything is still functioning properly.

05-26-2005, 05:03 PM
Gary, you have a very good point but didn't carry it far enough.

Where I live, no one but a qualified backflow tech can install one of these little guys. The homowner has to have the device, for irrigation, tested every 5 years , once again, by a qualified tech.

Gary Swart
05-26-2005, 09:08 PM
We (homeowners) can install them, but they must be inspected yearly.

05-26-2005, 11:24 PM
Anyone can install a residential one, and only commercial ones have to be tested yearly, or at all.

05-27-2005, 12:36 AM
This is not a major thing, but municipalities tend to make them a much bigger deal than necessary. I mean think of it: A backflow prevention device is intended to protect the occupants of that specific dwelling. If it fails or ceases to operate, it endangers no one but those occupants. It's not like you are releasing chloroflourocarbons into the atmosphere or endangering the life of your neighbors. Its sole purpose is to ensure that if a dog poops near a sprinkler head, it will not be backflowed into your drinking water system. And as such it is a very good thing to have, and you should definitely install it. However, I liken it to riding a motorcycle without a helmet or driving without seatbelts. I definitely use a helmet and always have my seatbelt fastened because that is the safe thing to do. But I don't think it is the government's place to force me to do so. If I don't it only harms me, not Mary and Joe down the street. Am I making sense or should I zip my lips (fingers)?

Public places such as buildings and shopping centers definitely need backflow prevention devices and they obviously need to be serviced by qualified personnel, but private dwellings... ?

05-27-2005, 08:28 AM
That is absolutely wrong. In fact where they require BFP's on the main line it protects everyone in the city, except the occupants of that building. The entire city system is interconnected, and a BFP protects it from any contamination upstream. If it is connected to a irrigation system, then it protects the entire system, AND the house occupants, but it never protects "just the occupants" when installed in the manner we are discussing. I could cite numerous cases of system contamination, including the house occupants, when a BFP was not installed.

05-27-2005, 07:42 PM
Please do a little internet research on backflow prevention and you will find the case studies where entire neighborhoods have been poisened.

Frankly, the city is not overly concerned about whether you might poison your own bad self; but it is precisely because lack of a backflow preventer on your system could cause YOUR dirty yard puddle full of dog poo and, fertilizer, and diazinon to be siphoned into the city main ( under the proper set of circumstances) that they do make this an issue. The circumstances that can cause this , while not common, are real: You have your main valves open and the system valves turned on; the city main looses pressure due to maintenance or a rupture; it is not unusual now for the city main to have negative pressure, sucking anything available from your yard.

05-28-2005, 01:47 AM
I stand properly corrected. Don't ask me what I was thinking, but you guys are absolutely correct. Don't worry, I've already smacked my forehead...