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I am planning an above-ground system for a very small lot. I am trying ot do most of it with drip irigation, but I also have small lawn to the side, and I was wondering if I could combine the drip and lawn irrigation in one zone.

For instance, I have a section of the yard along the porch that has a 0.5 m strip of shrubs, vines, flowers, ground cover, and small decorative trees, and also about 3 m (10 feet) narrow section of lawn that is maybe 5 or 6 m long. I could theoretically run two lines alongside each other — one for drip, another for the lawn, but that would mean twice the tubing, twice the timers, filters etc., and twice the clutter.

I’ve found the stakes that work with standard 1/2" (13 mm) drip irrigation main, that has 1/2" threaded outlet, on which any regular sprinkler can be attached, either directly or via the riser:

1/2" flow-through stake

And so I could run my drip main along the edge of the lawn, interrupted by few of these stakes. And I could use those small 180° sprinkler heads, such as shrub sprinklers which are the same heads that are used in small pop-up lawn sprinklers for narrow lawns. But my two major concerns are water pressure and flow, and watering time.

For instance, those pop/up shrub sprinkler heads are recommended by the manufacturer to be used at four per zone at 30 psi (~207 kPa) based on the “average” rate of flow of 1.6 U.S. gallons per minute (6L/min) in a larger main pipe (such as 3/4"). At the same time, drip irrigation, as I understand, runs in 1/2" pipe at 25 psi (~172 kPa), and I am not sure it would produce enough flow for those shrub heads. That said, I am going to run them at the low end of their range, so that might help.

As for watering time, I wonder if they would saturate the lawn too fast (ideally, I am thinking in investing in moisture sensor to cut them off when it’s good enough, or to delay the watering after the rain), and it would cut the watering time too short for some full-size grape vines or decorative small trees, such as Japanese maple. At the same time the lawn is possibly the one part of the garden that receives a lot of sun most of the day (the rest is covered by catalpa, peach and cherry trees), so it would need longer watering as well.

So I need recommendation as to whether my idea is feasible (pending accurate flow measurement), or to direct me towards possible alternatives, keeping in mind budget constraints and water conservation.

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I was concerned about the flow in this application, because for my set-up four spray heads would need at least 360 U.S. gallons per hour (1.5 gpm × 4 × 60 min, 1365 L/hr), and the 1/2" tubing allows for much lesser flow. For instance, Dig Corporation’s Drip Irrigation Installation Guide specifies that the maximum flow rate in their 1/2" (0.600" to be exact, or 15.24 mm) tubing (one I am using right now) is only 220 gph (~830 L/hr) or 3.(6) gpm or around 40% less than necessary.

However, I decided to try it out, and see what happens. I’ve purchased the stakes, four spray heads, and short lengths of cut tubing (so that I can return it back to the shop, instead cutting up my own tubing). I had rigged up the following structure via the basic main assembly (back-flow preventer, filter, and pressure regulator), and decent length of the pipe to account for the internal friction losses in real-world application:

enter image description here

To my surprise, all four heads gave solid spray and decent reach with last drops getting to the distance of 3.6 m (12'). Obviously, the effective coverage may be somewhat lower, but still close to the specified maximum range of the spray heads. This looks like viable option for my application, and while I still am considering drip micro-sprinklers, it is nice to know that in that particular case the empirical evidence is more optimistic than basic theory.

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