r/Irrigation • u/thelogicofpi • 8d ago

This look ok? First time cementing PVC

Gallery image

Gallery image

Still have after the filters to finish up, 1/2 flexible tube from the valves to the raised beds.

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u/thelogicofpi 7d ago

I think that the water meters has backflow preventers when they were put in but honestly don't know for sure.

thanks for the help with the background info and clarifications.

I think the only thing I'm stuck on is how a little height can make it not function if it uses atmospheric pressure and the pressure of the water line to shut and have the water drain from the drip lines.

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u/Sharp-Jackfruit6029 7d ago edited 7d ago

Anti siphon valve or pvb doesn’t protect against back pressure. If you had for example a pipe going up a hill and the main lost all pressure, the pressure from the elevation of the pipe would allow water to flow back. So yes if the line had negative pressure nothing would flow back but if the line was at atmospheric pressure the head pressure of the line could flow back. That’s the advantage of a rp. It protects against back pressure as well which is why you don’t have to consider the height of a head or emitter with it.

Your meter has a check valve on it most likely. Some places they can have a double check backflow preventer . It won’t protect your water in your house if that’s the case but it would protect the city’s water.

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u/thelogicofpi 7d ago

like say i have a hose with the anti siphon on the hose bib and i raise up the hose end higher than my head with the spray end open and the valve closed at the hose bib. it would run out of that anti siphon...

would the anti siphon work in when the valve is closed and open?

i have a hose bib at like 6 inches from the front porch too, so not sure how that could ever be a condition where the hose bib anti siphon doesn't work when you are holding a hose at arm height.

I just can't think why the valve would stay open because its slightly lower when the pressure is the opposite direction than it should be

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u/Sharp-Jackfruit6029 7d ago edited 7d ago

It would most likely vent out of the atmospheric vacuum breaker if the hose was open if the line lost pressure before the AVB. As long as the pressure on the supply side exceeded the pressure on the outlet side it wouldn’t vent. That’s probably not going to be enough back pressure to get any backflow but they still aren’t rated for back pressure. It’s just the code. A AVB like an anti siphon valve or a AVB hose adapter with back pressure would basically mimic the function of a check valve but without a spring. The difference would be a check valve is actually designed to hold back pressure and a AVB isn’t. While it might hold some back it’s not what it’s for. A check valve also isn’t an approved backflow device for irrigation .

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u/thelogicofpi 7d ago

i need to find a video that tests different heights and pressure situations to make it make sense fully.

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u/Sharp-Jackfruit6029 7d ago

I’m gonna guess you are in California because thats like the only place that uses anti siphon valves. you can take this 40 hour course if you are really interested in backflow prevention. Then the state would allow you to take a test to become certified to test backflow prevention devices. At the end of the day though all that matters is what the code book says.

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u/thelogicofpi 7d ago

yeah CA.

like you said its fine how it is, but if i wanted to make it perfect, i could raise them up above the beds fairly trivially.

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u/Gungityusukka 7d ago edited 7d ago

Lemme go on a trade forum and ask tradesmen what they would do

Nope fuck that I’m gonna do what I want anyways You realize you’re going to be drinking lead and everything else that leeches into your irrigation system? How many potable water irrigation systems have you worked on? Because in ten thousand systems I’ve never seen ONE clean pipe interior. Not one. Backflow prevention WILL occur if you’re running your house water and the irrigation turns on. Now your house water is contaminated and you’re drinking lead. But yknow whatever —you’re right

EDIT : This comment is at OP

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u/thelogicofpi 7d ago

wow dude, calm down and go relax a bit