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coexist

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1

Thursday, March 31st 2016, 12:29pm

AVB's installation seems inccorect

Hi all,

I had a plumber replaced my external piping, with a an external faucet and AVB (Atmospheric Vacuum Beaker), and linking the line to my existing sprinkling system (white PVC on picture). What he did does not seem right to me as he only connected one side of the AVB. From my understanding (and how to was before), the output of the AVB was connected to the ingest of the sprinkler line. I have attached a picture to show the setup. To me, the AVB is useless here and will not prevent backflow. So looking to expert opinions. If you think it is wrong, how would you describe it so I can tell him it will not work that way.
Appreciate your help.

http://www.tiikoni.com/tis/view/?id=d30f63b

This post has been edited 1 times, last edit by "mrfixit" (Apr 1st 2016, 4:44am)


Wet_Boots

Supreme Member

Posts: 5,133

Location: Metro NYC

2

Thursday, March 31st 2016, 1:14pm

Your AVB does not belong anywhere in the plumbing. What the plumber might have done is to confuse "Vacuum Breaker" with "Vacuum Relief" (a device to prevent water tanks and water heaters from crumpling inwards from a vacuum.

What you probably require (supply your location, please) is a Pressure Vacuum Breaker, a more complex backflow preventer that is used when there are zone valves downstream of the PVB, and the entirety of the sprinkler system is at least a foot lower than the PVB.

coexist

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3

Thursday, March 31st 2016, 2:10pm

Thanks Wet_Boots. I am actually in New York State, Nassau county (long island), with I know strict code restrictions.
I will look into it actually, but do you think the AVB is doing anything here and if left would have any negative impact?

Wet_Boots

Supreme Member

Posts: 5,133

Location: Metro NYC

4

Thursday, March 31st 2016, 2:35pm

the AVB is a paperweight - nothing more - what you will end up with is something like the plumbing in the photo


coexist

Unregistered

5

Friday, April 1st 2016, 8:27am

Ok, understood for the PVB!
One last question on the AVB and existing setup. My main water line is shut-off right now and want to wait a couple more days to open it as we have upcoming freezing temperature.
What will happen when I will open the water line? Will the water come out of the AVB from the unconnected part (output)?
In a normal AVB installation (not for sprinkler let's say), the water will flow from the bottom (vertical) to the top (horizontal output), correct?
Cheers,

Wet_Boots

Supreme Member

Posts: 5,133

Location: Metro NYC

6

Friday, April 1st 2016, 4:38pm

You got it right. the AVB is just going to spew water from its outlet.

Fix the plumbing now, before the warm weather sets in and you can't get anyone out there in time.

hi.todd

Supreme Member

Posts: 480

Location: Houston, Texas

7

Saturday, April 2nd 2016, 5:13pm

Wow, That Was Lame

I can't believe that AVB Installation. It really makes you want to scratch your Head.
:thumbup: :thumbsup:
LI0006121, BPAT0011021, CI0009500

coexist

Unregistered

8

Tuesday, April 5th 2016, 4:14pm

Thanks guys. It is indeed lame and I still don't get how he could have installed it that way!

I just wanted to let you know that I quickly turn the water on while taking a video and got a big splash. The water is indeed coming out of the AVB as expected.
So I called my plumber (having a real proof of the bad installation) and despite not really understanding what is going on, he said that he put the same device that was there before (i.e AVB) but that I should normally need a double check valve. This need to be installed at the main water line, which in my case is really hard to do now as in a small wall enclosure.
So my next question before he came on Friday is:
- do you really have to install a double check valve at the main line or can it be installed right before the sprinkler line (but outside)?
- the best way would be to install a pressure vacuum breaker (cheaper than double-check valve and exterior installation possible), but what would be the drawback compare to a double-check valve?
It is crazy to have to double-check the work of a professional!
Thanks.

hi.todd

Supreme Member

Posts: 480

Location: Houston, Texas

9

Wednesday, April 6th 2016, 8:42am

Response

Local Codes will be the Authority of the day.
The Good news is that when a PVB is installed correctly (12" above the Tallest Sprinkler head, Piping, water outlet connected with no back Pressure) it is a better method of protection than the double check valve assembly. It is better because it is a High Hazard Backflow Preventer and the Double Check Valve Assembly is a Low Hazard Backflow Prevention Assembly.

This is not taking into account the potential for freeze damage. Many cities allow double check valves to be installed below grade, which is poor practice in my humble opinion. Because when you bury the double check it is usually going to be flooded out and the handles get rusted. When it is time to annual test the buried Double Check Valve Assembly there are possible contamination issues with opening and closing the test cocks with contaminated soil, water, debris. Often times the serial numbers on a buried assembly are un readable, the test cock handles don't turn, and many testers don't like to work on their knees. When it comes to compliance, in my humble opinion, few testers will actually get on their knees and actually inspect the double check valve the way that it needs to be inspected, (With Gauges). So when you bury it, its like saying it was good upon installation, but after that????

I would ask the code enforcement people that allow the double check valve, If they were not allowed to be installed below grade, would they still accept the double check as a backflow preventer installed above grade or would they switch to the Reduce Pressure Assembly?

I am fortunate that the city of Houston, does not allow Double Check Valves for Irrigation.

Please don't Forget, after the assembly is Installed, it will need to be inspected by a backflow inspector or Backflow Tester that is licensed to inspect backflow preventers. An inspection will weed out poor installations and assemblies that are not functioning correctly.
:thumbup: :thumbsup:
LI0006121, BPAT0011021, CI0009500

COexist

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10

Wednesday, April 6th 2016, 1:35pm

Thanks hi.todd!

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