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Over the last weekend, I installed the irrigation system for our vegetable garden which is square-shaped. I used 1/2" poly tubing for the main water supply line and then used 1/4" drip line with built-in 1 GPH emitter (12" spacing) for each row. For the connectors between 1/2" and 1/4", I used 2 GPH emitters.

Two problems however:

a) Very little water comes out of the emitters. The size of the spots watered by the emitters are so small.

b) Many vegetables still do not receive the water because no hole exists on the 1/4" tubing around those vegetables.

I am wondering what would be the easiest solution to fix this. Would just punching more holes on the 1/4" drip lines solve the problem? Or, should I use a larger drip line than 1/4" to deliver more water?

Also, I ran the irrigation system for 10 minutes. Should I run more?

  • Assuming they are performing as they should (which the "2 GPH as connectors" may invalidate) 10 minutes would only put out 1/3 of a gallon from each 2 GPH emitter, 1/6th (ie, less than a quart) from each 1 GPH. If a number of 1 GPH are being fed through a 2 GPH, they will all be sharing that 1/3 of a gallon. From your description, that means each row only got 1/3 of a gallon. – Ecnerwal May 21 '15 at 2:16
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That's an unconventional setup with the 2 GPH emitters as connectors and I think it may be the cause of the problem unless that's how the 1/4" drip line was meant to be fed but I think that's unlikely. Normally you would use a connector that punches into the 1/2" line to connect the 1/4" line which doesn't create any restriction in flow.

Typically drip systems run at around 10 psi and there needs to be a regulator somewhere between your 1/2" tubing and water source.

The 2 GPH emitters will be dripping into the 1/4" lines which may not be enough flow/pressure to feed the emitters in the 1/4" line.

How long you need to run the irrigation is going to depend on how you laid out the 1/4" tubing and what the rates are of the emitters but 10 minutes seems a bit low.

Also, don't poke holes in the 1/4" tubing. The holes that are currently there are not just holes. They're emitters that are molded into the tubing that are calibrated to deliver a precise amount of water and some have features to prevent clogging. Since you already have the 2gph emitters one thing you may want to do is just get plain 1/4" drip line without emitters and attach the 2gph emitters at the ends and put them near each plant depending on the size of your garden.

It would help if you could post a diagram of your garden along with the irrigation lines and where you have plants.

  • Thanks a lot. You're right. I should've used something else, not 2 GPH emitters. – DSKim May 20 '15 at 21:01
  • @DSKim the connectors you want have a sharp end that pokes into the 1/2" tube on one side and a barb fitting on the other that the 1/4" tube slips over on the other. If you set up a grid of 1/4" tubing with lines 12" apart and cover it with mulch it should provide adequate water. Run it for 30-60 minutes twice a week depending on how hot it is or how much rain you get. Emitters don't need to be right next to the plant but mulch is important to help retain moisture. – OrganicLawnDIY May 20 '15 at 22:10
  • Thanks. I've never thought about mulch. I will give it a try. – DSKim May 20 '15 at 23:57
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a) Those emitters appear to deliver very little water even when under the correct pressure, and they really only deliver to a single spot. Water must move through the soil to reach other areas, and the horizontal distance across which the water will move will depend on the soil characteristics, existing moisture content in the soil, and the duration of flow from the emitter - among other things.

b) although drip can be effective for vegetables when implemented properly, it is often simpler to use small spray or rotary heads (though these present their own problems for disease prone vegetables). As you mention, some plants along the drip line may not have holes near them. However "they" make tubing with different hole spacing. See if you can find one with more holes.

"Would punching holes in 1/4" drip line..." - although this would cause the hose to emit water at each of those locations, you wouldn't know how much it was delivering unless you measured it at each punched hole. You also wouldn't know how those holes might affect the calibration of the other holes. It might cause the other holes to deliver less than expected. Better to use tubing with holes spaced closer together.

and 10 minutes doesn't sound like enough time to let it run, but that would really depend on weather, soil type, the rating of the emitters and the tubing....

  • Thanks a lot for the advice. If the drip lines do not work out, I will try sprays as you suggest. – DSKim May 20 '15 at 21:10

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