118 comments on "....... We Wasted a Day of Sunlight!"
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Here's a note from a related application. Just put in a pond w/ 10-ft of head above a new garden spot and have been investigating drip irrigation techniques. Most commercial systems require 10psi (or approx. 23-ft head) to operate as designed. So . . . low head applications require a different approach. I'm headed towards 2" diam. siphon line from pond into undetermined diam. distribution lines.
I work alot with gravity systems. For surface water and drip, I've never had much luck. Cleanest surface water always has some sediment, which clog emitters within a season, even at 28 psi in my experience. Need a good filter. Another problem I've had is bacterial deposits clogging emitters. That black head in the sun is a perfect incubator at times. Chlorine drip? Not worth it. I use large emitters for trees, but in my opinion, the constant checking of emitters and risk of losing a young tree in the orchard is not worth it. Easier to dump 5 gallon buckets.
Low head is a problem. At about 20 feet of head, (never checked the gauge for psi) I've had luck with lightweight 1/2 inch thread plastic impact sprinklers on pasture. I run 1 1/2 poly for a mainline, then 2 1 inch laterals, trying to keep cost down. You should lower friction losses with your 2 inch. Also had luck with 2 3/4 inch head brass nozzles on each end. 1/2 inch brass, esp rainbird, I've never had much luck with. They just are too tight to spin properly. The biggest thing is keeping any air out of the lines.
For low pressure sprayers take a look at 'wobblers'.
At 10 psi they will throw a 24' - 30' circle of water and throw nice large drops that aren't blown about by the breeze.
I've been using them for a few years and am quite happy with them.
http://www.dripworksusa.com/store/sprinkler.php#tiptop
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Seems to me that going to 2" water line is going overboard. Unless you have a long run or are moving a lot of water it just doesn't seem necessary (or effective).
Check a micro hydro site for psi loss calculations.
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For a low cost drip system visit a local restaurant/bakery and get some (usually) free five gallon buckets. Drill a hole or two just above the bottom, set them beside a tree and fill with the hose.
The water will flow out slowly and get absorbed rather than running off. And you'll have some idea of how much you gave the tree.
I agree with your thoughts on 2 inch. On another gravity system I also use 1 1/2 for mainline, probably up to 600 feet on 30 to 50 feet of head, depending on lateral location.
As I recall, frictional losses between 1 1/4 and 1 1/2 are about double, worth the pipe cost.
Another line, though, at 1800 feet and wanting 15+ gpm, was worth the money for 2 inch.
Wobble link looks interesting, any problem with clogging? You using their 1/2 line and tubing? What is your water source? I tried years back a homemade system w/o emitters where I just cut tubing to length to get a desired flow. Had clogging problems with it on pond water, running about about 25 psi on lateral.
Thanks for the thought, but I don't have 10psi but rather 10ft of head. Much different energy gradient. Many more options become available at 10psi, such as the one you suggest.
My calcs are showing approx. 24gpm after losses for my 2" PVC trunk line. Intended application is 4000SF vegetable garden, so I'm thinking I could use all of that after I try to branch down a number of rows.
24 gpm on 4000 ft is one heck of alot of water. Might as well just go furrow flood.
As I haven't done this yet the feedback is interesting. Thanks.
By my calcs 24gpm on 4000sf work out to just over 1.5hrs to apply a uniform inch of water. I was thinking this was just about right, but you're saying this is too much?
24 gpm, about 5 garden hoses on full, can give you real erosion problems unless it's really spread out. Tubing would require a maze to cover 4000SF.
Furrow irrigation is the choice among growers with flat land and plenty of water, which you appear to have. It's quite effective, having complete field saturation, as opposed to overhead which tends to overwater certain areas while leaving others drier. It works best after the crop is established, as it often can destroy seedlings. Any slope and you are liable to get gullies.
If you are limited to 3 or 4 psi, and wish to conserve water, I suggest a small gas water transfer pump, assuming the pond is too far from electric power. They usually will run a couple hundred. Like a chainsaw, the few liters of fuel it would consume are quite worthwhile in operating sprinkler or drip systems. Perhaps there are now reasonably priced solar pump systems you might find.
If your pond is just established, you might wish to wait a year to get a handle on its seal and evaporative losses. That could point you in a different direction, with some pond evaporative losses exceeding an inch/day.
Thank you very much for the advice, it's much appreciated. Would you have any particular reference sources for irrigation practices? Email address? I have a yahoo email account under the name 'onewoodturkey'.