Planning and Laying Out a Low Flow Irrigation System
Plants, lawns and gardens all need water to thrive, but the sprinkler systems most of us use to water them are really inefficient. Just think about it, you throw a small stream of water up into the air where the wind can get hold of it and blow it over onto a sidewalk or road. Plus, unless you are carefully timing how long you run your sprinklers, a lot of the water that lands on the ground forms into puddles and evaporates before it ever soaks into the ground. So obviously you end up wasting a lot of water.
Low flow irrigation systems don’t have either of these disadvantages. The water is delivered in limited and correct quantities to the right locations so it can do the most good. The efficiency of low flow systems is shown by the fact in some areas of the country during the heat of summer, low flow watering in the only method allowed for watering gardens.
For most homeowners the downside to a low flow system is often the fact they don’t know how to lay out plan a system so figure they need to hire a landscaper to do the job, and that usually translates into big $$$. However, if you’re willing to take the time to do some up front planning you can have an efficient low flow irrigation system working in their yard for a few hundred dollars. Here’s how you can plan your own low flow irrigation system.
Information and components of low flow irrigation system are readily available at most home and garden stores including how to assemble the components and their water requirements.
Here’s an idea of the basic components of a typical system; the quantities will obviously vary depending on the size of your gardens.
- A header hose equipped a faucet connector (usually ½ or 5/8-inch plastic tubing).
- Backflow preventer (to stop water from potentially flowing back into your home water system.
- A pressure regulator (ensures consistent pressure for watering, since water pressure in municipal systems can vary from 30 psi to 70 psi in some instances. For your system to work properly the water pressure needs to be consistent).
- Depending on the layout of your gardens, possibly some feeder lines (usually ¼” plastic tubing).
- Compression ends to stop water from flowing out the end of your header hose.
- Various emitters (i.e. misters, full circle sprayers, ½ circle sprayers, ¼ circle sprayers). In preparation for planning your system, go to your home store and get a description of the various types of emitter available, their spray pattern and how much water they consume.
- You’ll also need some other pieces such as tubing cutters, and potentially connectors and elbows.
Your next step is figuring out how much you have available.
You need to calculate the water flow that’s available in order to design your basic system and determine how many drippers and sprayers you can install on a single feed line. This sounds complicated, but really all you need to do is run water from your outdoor tap into a five-gallon pail and time how long it takes to fill up.
If the pail fills up in two minutes, you have 2 ½ gallons per minute (or 150 gallons per hour). Be sure no one is running water in the in the house is running water while you do your test or your estimate of available water will be wrong.
Now, since your system is likely going to include components like filters, splitters and backflow preventers that will all restrict total water flow, estimate your effective available flow at 10% less than your unrestricted measured flow.
Now that you know the water flow available to you, you can lay out your system on paper.
Measure the garden and plant areas you want to water and draw them to scale on graph paper. Consider the types of plants in each area and their varying water requirements.
Now mark in the emitter locations and type of spray pattern on your rough layout, keeping in mind the plant’s water requirements and the different spray patterns of emitters relative to sidewalks and roads.
Tally up the water requirements of all the emitters you’ve included on your plan. If the total requirement is less than your available flow rate, your layout will work. However, if your layout requires more water than you have available, you will need to modify your plan, creating two (or more) watering zones, each of which can be accommodated by your available water flow.
Once you’ve got your system designed all that’s left is to purchase the pieces and put them together. The plastic components are quite easy to work with and a system can usually be put together in a weekend. After that, you and your gardens are on your way to a green, water efficient summer.