# Need some design help with irrigation valve box & freezing/drainage



## rossn (Apr 10, 2019)

Hi,

I need a little help with my irrigation valve layout and drainage and preventing freezing. I'm located in the Denver area, with frost line ~30".

*How should I lay out my two (17x23) control boxes to prevent freezing to city water supply for ouse(green line, about 33" below grade), well supply line to house (just above and parallel to the green line and about the same elevation), and manage drainage?*

#1-4 & D (in the photo) are maybe 14" below grade (D maybe 1" lower than the others) and based on a water test, I think they go up slightly as they head away from the pit area.

*How do I handle drainage, if I'm trying to avoid having to blow out sprinklers seasonally? Originally I thought D would be a gravity drain to the spigots, but testing with water, I think it must slope up a little first and so there is not natural escape for drainage*.

In the photo I have:

A: City water supply for BFP
B: Downstream of BFP, where copper will drop to a threaded el
C: Well
D: Blue 1" Poly leading to three seasonal spigots, each with a drain valve about 18" under ground... they are arranged so one end spigot is at the highest point, and one end spigot isat the lowest point. This area is between the first two spigots.
X: Ignore
1: One zone, 1" Poly
2: One zone, 1" Poly
3: One zone, 1" Poly
4: One zone, 1" Poly
5: One drip zone, 3/4" Poly
6: One new drip zone, 1" Poly
7: One new drip zone, 1" Poly
8: One new drip zone, 1" Poly


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## robertmehrer (Feb 28, 2019)

for me, i dug down about 12" below the lines under the clay and into sand. I then got drain field rock and lined the bottom 6" with that, and then put smooth river rock above that. The valves and lines sit on the smooth river rock. However they move around with water hammer, keep that in mind. Since ive done this my boxes dont fill with water anymore. I had an issue with them filling up with the two heads next to them just spraying water into them. About 4 feet away is the yards french drain and it quickly collects the water from under the boxes.

Just a suggestion.


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## SCGrassMan (Dec 17, 2017)

You live in Denver, with a 30" frost line, and you're looking to avoid blowing out the lines?

Did I read that right, or is there something I'm missing here?


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## rossn (Apr 10, 2019)

Yep, you read that right. The irrigation system was in place for about 20 years, and according to the owner, he only ever did some gravity draining. That would be the ideal situation, though some of the poly seems to still flow towards the valve box even at the original installed height.


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