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Rosedoc

Active Member

Posts: 7

Location: USA

1

Saturday, April 21st 2007, 10:24am

Backflow/Antisiphon Questions

I have a non-potable water supply system totally separate from my potable domestic system and contamination of the irrigation supply system is not an issue. The water in the irrigation system is not real clean since it originates from a stream. It is pumped to a holding tank approximately 400' elevation gain and gravity fed to my irrigation system. I get 15 gpm and 40 psi at my zone boxes.

Question #1: Can anyone tell me the pros and cons of not installing backflow or antisiphon devices on my new irrigation system? I have 4 zones coming from one zone box and 6 from another. I anticipate additional zone boxes running from this system in the near future so I want to get this right the first time.

It would be very difficult to install the valves or any antisiphon devices higher than the sprinkler/drip heads on these irrigation zones and I can't afford the pressure loss an RPB valve (I think that's what it's called).

Question #2: If I installed a double-check valve, can I install one to cover each zone box or would I need to install one for each zone? If I were able to install just one DC valve to cover all the zones in a zone box would I run the risk of damaging my zone valves since I assume the DC valve would install in front (before) any of the zone valves. (I hope this makes sense to someone out there.) I'm planning on installing one of those new Rainbird Quick-Check filters before the zone valves and before a DC valve. Would this work satisfactorily?

Question #3: Has anyone had any experience with these new Rainbird Quick-Check filters? Can they be installed in front of the zone valves in the zone box or would I need one for each zone?<font face="Tahoma"></font id="Tahoma"><font face="Courier New"></font id="Courier New"><font color="blue"></font id="blue">

Thanks so much for any advice/suggestions about this possible (or impossible) installation!




Tom

Supreme Member

2

Saturday, April 21st 2007, 11:28am

If there is an air gap between the pipe feeding your tank and the tank itself there is no need for a backflow device. The air gap is the backflow protection.

Rosedoc

Active Member

Posts: 7

Location: USA

3

Saturday, April 21st 2007, 12:14pm

Thanks, Tom, for your response. There is no air gap between the pipe feeding the tank and the tank itself.

I neglected to mention that this tank on top of the hill feeds an extensive system of hydrants and I'm just tapping off of the hydrant supply line closest to where I need this new irrigation system. In other words, there is no dedicated line from tank directly to the new irrigation system. So the supply line to the new irrigation system will always be charged. . . . or am I misunderstanding what you're telling me?

HooKooDooKu

Supreme Member

4

Saturday, April 21st 2007, 6:40pm

The Rainbird Wye filter I'm using (and was told would be fine for mainlines) is rated at 150psi, and I see that the filter you're talking about appears to be too. So if you install a DC, you should install the filter before the DC so that trash in the lines doesn't foulup the DC.


Rosedoc

Active Member

Posts: 7

Location: USA

5

Saturday, April 21st 2007, 7:08pm

Thanks HooKooDooKu for your help. I think that's what I'll end up doing--install the Rainbird Basket Filter, then the DC valve, then my zone valves. That ought to cover it.

My thanks once again to you, Wet Boots, Tom and HooKooDooKu for your sage advice. It's much appreciated by me and, obviously, by so many of the other folks posting on this site.

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