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A “drip irrigation” system will automatically keep your garden well watered; it not only is an efficient way to water plants but also saves you time and ensures consistent watering when you’re busy or out of town. Learn more about how you would plan and install a drip irrigation system.
What is Drip Irrigation?
Drip irrigation is the slow, even application of low pressure water to soil and plants using plastic tubing placed directly at the plants root zone.
It’s a very efficient way to use water because the water goes straight to the plants without evaporation or runoff. Plus, the water is at the root level so there’s no wetting of leaves from sprinklers; constant water on cultivated vegetable leaves invites disease and is also very wasteful since water quickly evaporates, never reaching the roots.
Also, there’s the convenience factor! When you are on vacation or simply away from your garden, drip irrigation can be set up with a timer to deliver water consistently.
Water not only hydrates plants (as it does humans) but it’s also the way nutrients are drawn up from the soil through roots and stems into leaves and fruit. So, good irrigation is a high priority in gardens – as important as strong sunlight for most crops!
DIY Drip Irrigation
A lot of gardeners water little and often. This is great for small seedlings but once the plants become larger it can mean that only the top inch of the soil is ever dampened. For crops that put down deep roots, watering more heavily but less regularly can help build up reserves of moisture deeper in the soil, making them more resistant to hot dry spells of weather.
To reduce evaporation, add a dry mulch on top of the soil such as a thin layer of dried grass clippings, comfrey leaves, hay, straw or wood chip. Water can seep through this layer but it doesn’t evaporate quickly and the soil below is kept moist. If you suffer from slug damage in your garden, it’s best to only apply mulch during summer as during damp seasons slugs can multiply under the protection of soft mulches.
For big plants such as tomatoes, burying a plastic bottle with a few small holes punched in the bottom can provide an extra water reservoir. Screw the cap on the top and water will slowly percolate out into the surrounding soil, providing a consistent water source. Combine this with guttering and water barrels and you can end up with an eco-friendly solution that stores excess water during wet weather that you can use efficiently during dry periods.
Planning a Drip Irrigation System
The most efficient way to irrigate crops is with “drip irritation” in which you automate the watering using a timer and delive water exactly where it’s needed.
Most drip irrigation systems start with three things at the water source:
A timer which controls when the watering should happen. Typically, this will be 10 to 15 minutes in the morning and/or evening.
A filter to ensure that nothing passes through that can clog up the drip irrigation holes.
A pressure regulator which will prevent the water pressure exceeding what the drip pipes can handle – usually around 30 PSI for a small garden.
To pipe water to where it’s needed, half-inch supply tubing is ideal as it’s easily fixed to walls, cable-tied to other pipes or buried under pathways to avoid tripping over it. It’s important to identify any sharp bends as this could restrict water flow if the tube kinks. To prevent this, it’s usual to cut the tube and insert a 90 degree elbow at each corner you have to go round. T-junctions can be used for line that comes off the main supply and each length needs to be finished with an End.
Once the supply tubing is in, it’s time to add the drip line. The easiest way to do this is to punch a hole in the main tubing and insert a transfer barb which feeds thinner quarter-inch tubing up to where the water is needed. This is then connected to quarter-inch dripline to supply the plants.
Several different patterns are commonly used when laying out the tubing. For plants in rows, dripline is run along the beds, kept in place by U-shaped hold-downs every 3 feet or so. For more densely grouped plants you might choose to snake the dripline along the bed.
Note: If you have the Almanac Garden Planner, you can plan drip irrigation by selecting the Irrigation layer from the toolbar. This makes it easy to work out just what you require. In our Garden Planner, you can draw this by holding down the Ctrl key on a PC or Cmd key on a Mac to add lines for each quarter turn, then curving them using the middle handles. For square or circular beds a spiral layout can work well. Containers on a patio or deck can also have lines branch out to them.
Whatever pattern you use, the rule of thumb is that quarter-inch dripline can only feed around 15 to 20 feet, so if you need to go longer than that you’ll need to run another length from the supply tubing. Larger bushes and trees will often have their own supply, either half-inch emitter tubing or, if they are spaced out, you can use half-inch supply tubing with emitters inserted into it. Circle the tree so that roots are encouraged to grow out rather than stay in a tight rootball.
Finally, it’s fine to put a layer of dry mulch over the dripline as long as it doesn’t become buried into the soil which can cause back-suction of dirt, causing the drip holes to get clogged up.
These simple design principles work well for small to medium gardens with an equivalent of up to six 4’x8’ beds. For larger gardens, you’ll need to run more than one supply line and consult your supplier to calculate whether the water pressure you have is sufficient.
Note: If you’re using our Garden Planner: When the design is complete, just click the Parts List button where the Garden Planner has calculated the number and length of parts required. Add around 10% to the totals for any lengths of tubing to make sure you have a little spare when installing it. With your plan and parts list, you’ll find it much easier to put in place a reliable system to ensure that plants get the regular watering they need.
Catherine Boeckmann loves nature, stargazing, and gardening so it’s not surprising that she and The Old Farmer’s Almanac found each other. She leads digital content for the Almanac website, and is also a certified master gardener in the state of Indiana. Read More from Catherine Boeckmann
Very informative. Have been thinking for last 2 years, but never ventured for the 600 sft+ garden.
Some clarifications are needed.
How to lock the drip line at the end of 15’
What is the spacing of holes to be punched on supply tube - should they be staggered if I plan drip lines on either side of supply line?
What is the max length of supply line? From my faucet I need to run about 120’ till the other end of garden. ( garden starts at 60’ point, which length obviously needs to be buried. )
I have long runs of drip line on landscaping plants out by the highway. I planted the plants spaced according to how big they will eventually get. I then just punched a hole in the main drip line and inserted the drip plug. I use 2 gph and 4 gph flag emitters, depending on the individual plants needs. I dug relatively good sized caldera at base of each plant to contain the irrigation water and not run off and water weeds. I placed the drip line with the emitter under each plant. It works fantastic. I've had them in for about 4 or 5 years. At the frost free faucet, the 1st item in the line is a pressure regulator because we have really high water pressure on our home well. Then I have a copper "splitter" so I can run the north line or the south line. If I am going to be gone on vacation, I simply install a timer between the pressure regulator and the copper splitters. When I go out and water, I simply walk along and you can hear or see the water pooling in the caldera basin around each plant base. I do a little weeding while I walk from beginning to end. If an emitter plugs for some reason, you can tell and fix it immediately. By the way, I've only ever had 2 emitters plug and it was easy fix. I loosen the end cap on each line at the end of irrigation season and pull one emitter plug from the lowest point on each line and let it gravity drain the water for the winter. Next spring just tighten those end plugs and put the 2 emitter plugs back in and you are good to go.
We’re not expert on drip irrigation and would refer you to an irrigation supplier. But we’ll offer up our best understanding:
—End Plugs are available to terminate a line of drip irrigation but any method of sealing the tube should work.
—Spacing depends on the type of supply tubing (which is sold in different diameters) and how long it is being run. 1 foot spacing is commonly used but there are many variables. Again, best to consult the supplier.
—120’ should be fine for supply line, depending on the pressure from the faucet. The main issue is loss of pressure from emitters and drip line and, again, the supplier will be able to help with calculations around that.