LBHS: Sprinkler Conversion

Right up there with weeding and deadheading, irrigation maintenance is one of those garden jobs that never really goes away. The task of replacing sprinkler heads, broken emitters, and stretches of punctured drip line is both urgent and important and the problem pops up more frequently than anyone is happy with.

Often times, students (and maybe just people in general) are intimidated by these tasks and are quick to either pass the problem off, or ignore the problem completely. Perhaps for fear of getting wet, the average student is not interested in fixing irrigation, go figure.

However, it is an important skill for at least one student in the garden to know, so, in the following post I have outlined a lesson plan about sprinkler conversion. My logic is that if the students can build the irrigation system, they will know when something is wrong with it. After problem diagnosis, I can then teach the skills they need to fix the specific issue.

Workshop Details:
2 day activity- total 2 hours (30 min. discussion and 90 min activity)

Workshop Goals:
Teach students the importance of water conservation in addition to practical irrigation repair skills.

Required Materials:
-measuring tape
-graph paper
-pruning shears
-* 1/2" x 3/4" bushing
-* 3/4" elbow joint
-* 3/4" 15PSI pressure regulator
-* 1/2" compression tube adapter w/ 3/4" pipe thread
-** 1/2" poly-tubing
-***appropriate joints and end caps for poly-tubing

*you will need 1 part for each sprinkler head that you are removing
** poly-tubing is usually sold in 50 or 100 ft lengths (purchase after measurements are made on day 1 of activity)
*** poly tubing joints are either T-joints, elbow joints, or couplings (purchase after garden layout is determined on day 1)

In this two day activity, I spend the first 15 minutes talking about why it is important to conserve water and where the water comes from. The second half of the discussion I gave an overview of the project and explained the role of the students  in the plan. Then we got to work.

Background information:
What is groundwater, and where does it come from?

The soil holds water in the spaces between grains of sand, clay, and gravel. Where the water fills up all the available space between the soil particles, we say the ground is saturated. We use wells and pumps to tap into this saturated layer, and if we pump the water out faster than the well is being replenished, the groundwater supply shrinks.

Over time, the ground that was once saturated becomes dry and collapses under the weight of the soil above it. As you can see in this famous picture of the San Joaquin Valley, CA, the ground has shrunk almost 60 feet since 1925. Once this ground has collapsed, it cannot be put back. As a result, the maximum amount of water that the soil can hold decreases and there is less water available for the future.

Why do we need to conserve water?

We need to conserve water, so that we can continue to grow crops in the future. Increasing our collective water use efficiency, both in the field and in our homes, is an easy way to reduce waste and preserve our future.

So, who is excited to switch our wasteful sprinklers to a more water efficient drip system now!

Activity Instructions:

As I mentioned earlier, The activity is broken into two separate days. The first day, students will measure sections of the garden that will be maintained by drip irrigation and dig shallow trenches where the poly-tubing will be laid. In addition to recording the length of the trenches, the students will determine the correct number of T-joints, elbows, and couplings that need to be purchased.

As an instructor, you should give the majority of the students their digging instructions first so that you can spend your time making sure that the measuring team is successful. Make sure that the students systematically stack the piles of dirt onto one side of the trench. This will ensure that the soil can systematically be put back once the poly-tubing is laid in the trenches.While most of the students are occupied, assign a group of 3 students to measure the length of the areas where poly-tubing will be laid. Have one of the students record the lengths on a piece of graph paper. I suggest drawing the irrigation plan on the graph paper. This will make the objective more clear for the students. Finally, allow the students to tell you which joints are required to connect the different limbs of the irrigation system.

On the second day, have the students finish digging the trenches, if they have not already done so. After the trenches are completed, break the students up into 4  groups. One group will layout the poly-tubing and cut the pipe using a pair of pruning shears, while another group will connect the poly-tubing using the appropriate joints. You will need another group to start filling in the trenches where the tubing has already been laid. Finally, you will need to assign the last group to rig the sprinkler head up like shown in the picture adjacent to the "Required Materials" section of this post.

I suggest keeping a close eye on the group that is assigned to convert the sprinkler head as it is likely they will be the quickest with their questions. In my retrofit, some of the sprinklers were connected to a 1/2" riser instead of the 3/4" pipe depicted in the required materials picture. As a result we had to insert a 1/2" x 3/4" bushing in between the sprinkler riser and the elbow joint to make the rest of the parts fit on top of the riser.

Please leave comments if you have any questions! Good luck and have fun!