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Drip irrigation troubleshooting

Posted by jkg51781 none (My Page) on
Tue, Jul 2, 13 at 12:45

After a lot of research I installed a drip irrigation system consisting of 75ft of ½” mainline, bubblers and pressure compensating drip emitters. The system has a 20PSI pressure regulator and filter and back flow preventer. The system contains 5 bubblers (2 gph setting) and 10 0.5 gph pressure compensating emitters. Each bubbler is connected to the ½” mainline via 2ft sections of ¼” tubing. Each 0.5 gph pressure compensating emitter is connected to the ½” mainline via 2ft sections of ¼” tubing. The system runs over level ground.

When I turn the system on, the bubblers work as designed, however nothing comes out of the pressure compensating emitters.

Here’s the part I can’t figure out. If I remove the end cap at the very end of the mainline, and let the water flow out of the mainline uninterrupted while the system is running, the whole system works properly, the bubblers work as designed and the pressure compensating emitters drip properly. As soon as I replace the end cap at the very end of the mainline, the pressure compensating emitters stop dripping. This leads me to believe it’s a PSI or Flow issue.

I tested the pressure at the faucet and it was 70psi

I tested the pressure directly after the pressure regulator and it was 70psi (this puzzles me)

I tested the pressure multiple times at the end of the ½” mainline (with the bubblers turned off) and it was consistently 20psi.

I then calculated the maximum flow from the house. The average flow at the faucet is 9.31 gpm, or 559 gph.

I then calculated the maximum flow from the very end of ½” mainline drip tube with the bubblers turned off) and it was 6 gpm or 360 gph.

I’m at a loss, I’m thinking it’s a pressure issue, however when I tested the pressure at the end of the mainline it was 20psi.

Any advice would be greatly appreciated.

Follow-Up Postings:

RE: Drip irrigation troubleshooting

You are someone who knows hydraulic theory and likes to calculate the troubleshooting of the issue. I am thinking in a different tack. If things don't make sense, I revert to trial and error methods if it is not too expensive. Here is my $0.02. My opinion may not b e totally accurate but so what. When you open the end of the 1/2" line you drop the pressure for the emitters to near zero and they work. This leads me to believe 20 psi is way to high for your pressure compensating emitters. You, in essence, are doubling regulating the line. Most drip system work at optimum at 10 to 15 psi. So the issue is two different types of drip on the same system. The bubblers don't really care what the pressure is (with in a range) but need flow. The emitters are the opposite. So to get to the point, change the emitters that aren't pressure compensating or reduce pressure to 10 psi with an additional in-line regulator or separate the two types of drip and reduce the emitters to a lower pressure or change them out. Those type are generally called torture-track(that's how they internally regulate pressure) and tend to clog reasonable quickly. With a level area, you don't need that type of emitter. There are many ways to go. So let us know what you tried and if it works out. JMHO Aloha

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