May
07
2014

Designing and Building a Drip System

Designing and building a drip system can be a scary thought for many gardeners. But it’s not really and we here at Gardening Unlimited encourage you to consider it. Our goal is always to help you achieve the garden of your dreams and a properly maintained drip system is often a valuable asset. If you could do something that would save you time, increase the growth and didn’t take a lot of money or effort, why wouldn’t you? In this article we will walk you through the process of buying the right materials and putting them together to make yourself a drip system that suits you and your garden’s needs.

Water supply and feed lines

The first thing you must think about in a drip system is where is the water going to come from. Outdoor gardens are easy as most people will simply get water from a spigot. Indoors you will have to purchase a water pump and reservoir or water tank. What’s important is matching your pump to the number of drippers you plan to use. The more drippers you plan to have the stronger your pump will need to be. Standard submersible pumps up to 1000 gallons per hour should be sufficient for up to around max 80 drippers. Of course smaller pumps will do less drippers and larger pumps do more. If doing more than 80 drippers you should invest in a sump pump or magnetically driven pump over 700 GPH since these pumps have more head pressure. If you have 2 pumps that both do 500 GPH but one has twice as much head pressure, expect that pump to do approximately 75% more drippers than the the other pump.

The next thing to decide on is what material to use for your main feed lines. Choices are PVC pipe, poly tubing or vinyl tubing. PVC and poly tubing are most commonly used outdoors while vinyl tubing is most common indoors. Here’s a breakdown of how and when they are used:

PVC Pipe – Very common in greenhouses and larger outdoor farms. Not very common for the home gardener. PVC is inexpensive, long lasting and comes in larger diameters for maximum head pressure which is important in large applications. Use PVC connectors to make necessary bends in your layout. Seal all connections with a PVC cement.

Polyethylene Tubing – Polyethylene, or poly, tubing is what you most people likely think about when they think of drip tube. Poly tubing is very common outdoors in small to medium sized gardens and often in large non-commercial gardens. It’s a semi-rigid black tubing with thin walls that can be bought from ⅜” – 3/4” in diameter. Larger sizes are available but most people will be fine using ½” poly tubing for any garden with up to 150-200 drippers. Helpful hint: leave poly tubing in the hot sun before trying to straighten out. Use barbed connectors or compression fittings to make any necessary bends in your layout.

Vinyl Tubing – Vinyl tubing is popular for indoor gardeners because the thick vinyl walls of the tubing are less likely to leak at the drip sites which can cause damage to indoor settings. It is available from ¼” – 1” diameters. Larger diameters can be very difficult to puncture and install drippers. ½” vinyl tubing is the most popular. Use barbed connectors to make any necessary bends in your layout.

It’s very important to make sure that no dirt gets into your lines as you are putting it together. I recommend taking extra precaution when laying out your feed lines by plugging or temporarily taping off any open ends. The most common ways to close off the ends of your tubing for good are:

  • End Cap – screws onto the end of the tubing.

  • Flush Valve – A valve placed at the end of the tubing that can be opened to flush the lines.

  • Manually – Simply bending 4-6” of the end of the tube and securing it to itself with wire or a zip tie usually works just fine.

When setting your lines it’s important to be aware of A) How many drippers to you plan to use and B) how much feed line you plan to use. As a general rule of thumb, do not use more than 400 feet of overall length per drip system. The diameter of your lines can be determined with the following scale. Total all your drippers and come up with an expected gallons used per hour and divide by 60 minutes.

Flow Range in GPM

Mainline Pipe Size

Lateral Line Size

0-3

1/2″

1/2″

3-6

3/4″

1/2″

6-10

1″

3/4″

10-20

1-1/4″

1″

20-30

1-1/2″

1-1/4″

Connecting water to the feed lines

Once you’ve chosen the material and diameter of the feed lines you can connect them to your water inlet. Water pumps will need an adapter to go from the pump’s water outlet side to a side with a male end that you will insert into your tubing. It’s a good idea to use an inline filter to remove sediment even though most pumps have a built-in mesh filter. If you are outdoors and using a spigot you will need a few more items; a backflow preventer, a pressure regulator and a Y filter. Here’s what each does:

Backflow Preventer – This item will help prevent water contamination from soil-borne diseases by not allowing soil and dirt to get sucked back up into the system when the water pressure turns off.

Pressure Regulator – Too much pressure will cause systems to drip unevenly. Most drip systems work best in roughly 15-25psi. Most homes have a psi anywhere from 40-100psi. Pressure regulators for your are cheap and buying one is an easy way to make sure there will be no problems later.

Y Filter – This item filters out any sediment that can clog drip emitters. Y filters have a removable screen that can be checked and cleaned regularly. Like pressure regulators, Y filters are inexpensive and worth the small investment.

If you are using poly tubing you will also need to buy a tubing adapter to connect your tubing to the pressure regulator or filter.

The last item you will need is a timer to run the system. While this is not necessary, you can turn the system on manually, it is recommended. Indoors you can use a standard digital timer that you will plug your pump into. Outdoors they make special waterproof timers that screw onto your spigot or hose. Both of these timers can be set for multiple waterings per day if necessary.

Choosing and installing drippers

The emitters are what control how much water each plant will get. When growing multiple varieties on the same drip system you will have to add more drippers or drippers with a higher flow to the plants that require more water. Some people don’t use drippers at all and prefer to use open ended ⅛”, ¼”, ⅜” or ½” tubing at each plant site. When adding drippers to the feed line you will want to purchase a punch tool to make holes in the feed line. This is important as making the hole too big causes leaks that can’t be fixed.

There 2 types of emitters; Pressure compensating and Non-pressure compensating. The first equals the pressure out for even flow while the latter does not. However, unless your system changes elevation by more than 5 feet you will probably be fine using Non-pressure compensating drippers. Here are the different dripper options for watering each plant site.

Spaghetti line – Spaghetti line doesn’t actually drip. It’s ⅛” or ¼” tubing that runs from the feed line to the plant site. ⅛” line can go directly into the feed line and is more common indoors while ¼” tubing will need a barbed connector and is used indoors and outdoors. A variation of this style of water delivery is to use ⅜” or even ½” tubing to the plant site. This delivery system will often need to be timed down using a periodic timer or a digital timer that can be set down to the second to avoid overwatering.

Turbulent Flow Emitters – These are the round disc emitters you see most often in residential outdoor drip systems. Common pre-set flow rate are 1/2gph, 1gph and 2gph (gallons per hour). You can also use an inline valve to send less water to certain sections of the system. This can be very helpful when you have different varieties in the garden. Example: Half gallon for strawberries, 1 gallon for tomatoes and 2 gallon for watermelon, bing, bang, boom. These type of emitters are pressure compensated and work great whenever water pressure is at least 10 or 15psi. Indoor drip systems that use a pump will most likely not have enough pressure in the system to use these drippers unless using a very powerful pump that can maintain pressure above 10 at all times. Remember, pressure can always be increased by using larger diameter feed lines.

Flag Drippers – These drippers can be individually adjusted for proper flow at each plant site. These work well with low pressure systems but clog fairly easily. They do come apart for easy cleaning but ideally you want a dripper that very rarely gets clogged.

Adjustable Flow Emitters – Similar to flag drippers, these can be adjusted for heavier flows. Since flow varies greatly they do a weak job of compensating pressure. Higher flow rates mean you shouldn’t use too many on one system or you risk dramatically uneven flow rates.

Now that you’ve laid out you feed lines, attached them to your water supply and installed your drippers it’s time to turn it on. As it’s watering walk the system and check each site for the correct drip rate. They make goof plugs if you need to remove a broken dripper at anytime. Make sure you have goof plugs and extra drippers, you will need them.

If you want some more in depth information regarding drip systems there are many good books about drip systems here and here for those who want to take their drip system to the next level of design and sophistication. It’s already May so if you haven’t got your starts going and you want a nice garden this year, you better get planting soon. Like Ernest Wilson said, “There are no happier people than plant lovers and none more generous than those who garden”. Have fun!

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