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Old 04-28-2014, 10:34 PM   #1
AdrianH
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Default Do valves gravity drain?

Hi. I am designing a irrigation system and am making it gravity drained so that I don't have to pay someone to blow it out for the winter. I have been wondering though if I am going to run into problems were various valve types do not draining the way I hope.

Now it is obvious that things such as my back flow preventer will trap water in between the double check valves, but I believe i can manually open the second check valve to let that drain. But for things such as my automatic control valves I am assuming that if left open they would drain whatever way they were tilted. I am assuming my pressure reduction valves would be able to drain from the outflow side.

What I am worried about is small chambers within the valve that are constructed in such a way that water will be trapped or pooled inside the valves even if gravity drained, and will expand in winter and burst. Or with the control valves, maybe it does not open and close like a door, maybe it is a check valve that loosens or tightens all the way when switched on or off, and therefore would not drain backwards even when left open.

Right now my design goes uphill from the water main to the backflow preventer, downhill to a manual drain valve, uphill to the controll valves, uphill to an anti sihpone, downhill to the sprinklers and downhill to a manual drain valve.

You can see how if my controll valves dont drain backwards then there is water traped between them and the anti siphon (the anti siphone has to be uphill sense it has to be the highest point)

Thanks for any help, feel free to ask me to expand on this if its unclear. I will be making drawings but wanted to get it at least somewhat right before I do cause I spend a long time on drawings.



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Old 04-29-2014, 09:24 PM   #2
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I`m thinking making it gravity drain just is not worth it. Running into all kinds of problems with valves needing at least some presure to get through even if toggled open. Electric compresors not that expensive.



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Old 05-03-2014, 03:07 PM   #3
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you're not going to gravity drain an irrigation system and get all the water out. Also, I wouldnt be comfortable just opening up the checks on my backflow preventer and assuming Ive eliminated the freeze potential. I'd blow out the system every late fall. I'd also install the BFP with unions on each side to remove it completely each winter and store it in a temperature controlled room.

Good luck

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Old 05-04-2014, 04:41 PM   #4
AdrianH
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Quote:
Originally Posted by jdc View Post
you're not going to gravity drain an irrigation system and get all the water out. Also, I wouldnt be comfortable just opening up the checks on my backflow preventer and assuming Ive eliminated the freeze potential. I'd blow out the system every late fall. I'd also install the BFP with unions on each side to remove it completely each winter and store it in a temperature controlled room.

Good luck
Thanks for the reply. How can I blow out my backflow preventer if it must be the first thing in my system. By that I mean I cannot install an air nipple upstream of my double check backflow preventer because that could introduce contaminants upstread of my backflow prevention. By the way in my town I only require a double check valve, no anti siphone required.
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Old 05-05-2014, 01:58 AM   #5
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The way Ive piped them is to put a ball valve on the outlet piping from the BFP, then a boiler drain. In the late fall, I can remove the BFP, shut off the ball valve, hook the compressor up to the boiler drain and blow out the system. The BFP sits in a heated mechanical room for the winter. In the spring, I just reinstall it.

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Old 05-05-2014, 04:08 PM   #6
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Thanks that sounds like a pretty good idea.



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