Small system...supply line pipe size?

15 years ago

This is a really small scale question, but I'd like to get it right and I know just enough about drip irrigation to be dangerous. ;)

Due to the heat and often drought conditions here in south Alabama (seems we're currently heading there again) we would like to set up a small drip system in a couple of 4x8 raised vegetable beds...and later tie into it to water a few blueberry bushes and a lavender bed. My plan is to run 3/4" pvc from the timer/filter to the beds. Once at the bed the pvc will go under the beds' sideboards and come up vertically just inside at a corner. A 90-degree elbow and a male hose fitting will go on the upright pvc and then hook to the 1/2" poly header. I will be using a 15 or 20 pound regulator and four 1/4" 6"-spaced .5gph drip lines per bed.

My question is whether reducing down from the 3/4" pvc line to the 1/2" poly will cause any pressure problems or other problems?

I definitely don't want to re-invent the wheel so any guidance is much appreciated! Thanks!

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Comments (3)

lehua49
15 years ago
dt,

What is your source water flow rate and pressure? Where is it coming from and how far is it to the beds and to the blueberry patch? What is the vertical elevation difference between your source and the various beds? Those are the factors to get it right the first time. I am already worried about the 3/4" pvc pipe used for the mainline. Is that line installed? Aloha
dirt_tracker Alabama Zone 8A
Original Author
15 years ago
lehua13, thanks for the reply.

The source is at the end of a 100' run of 3/4" pvc pipe where a standpipe and hose bib is located. That 100' run feeds off of the present (60 year old) house pipe network.

I haven't measured the flow rate or pressure yet...the deep well that my mother-in-law was getting her water from recently went dry and we tee'd off of our house (rural/municipal water) to her. This has resulted in a bit lower household pressure...probably ~50-60 pounds.

Negligible difference in elevation...rather flat terrain where the water is/will be running.

The 3/4" pipe is not installed yet. My plans are to extend the regular pressured line out to the area of the beds and from there plumb to the beds with lower pressure lines. Basically we're talking about maybe 10' of low pressure line going to the vegetable beds, maybe 20' of it to the blueberry bushes and 40' to the lavender bed.

If you need more info holler back at me.

Cheaha!
Ed
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lehua49
15 years ago
dt,

Sound like you have good pressure for your purposes except when you mother in-law is doing laundry or watering her plants. check the flow rate by filling a 5-gal bucket and record the time to fill. You are splitting your flow rate from the street with her when you are both using water. If your mainline from the street is 5/8" which is common for subdivision (1" for upscale homes), I assume your house is 60 years old, so you have a reduced size of piping to about 1/2" diameter(from scaling). This size give you about 14 gpm. You can verify this by the filling bucket method. If you have a demand from a 3/4" pipe while gardening and you and your MIL uses water you may experience lower pressure. To establish what that pressure is use a pressure gauge(cheap at Hardware Store) on a hose bid to monitor the pressure. I would put a 1" pvc to the beds to reduce pressure loss and go from there. Each fitting and regulator you install saps pressure, but you should be okay. You can always irrigate one bed at a time if necessary. A little wordy but hope this helps. JMHO Aloha