Container Drip Irrigation: Your Questions Answered

by Jerry McDonald
14 April, 2022
6 min read

Setting up a container drip irrigation system can be intimidating at first. Drippers, pressure regulators, drip stakes, manifolds, all of these pieces go together to spoon feed water and nutrients to your plants in the exact quantities needed. It's really quite simple with guidance from Grow Irrigation and the specialized products we have selected to offer on our website. Below we list several of the questions that commonly come up in setting up a drip system for the first time. Use this as an overview, and feel free to contact our technical experts for answers to questions specific to your operation.

What is a CNL Dripper?

Most of the technology of a drip irrigation system is in the pressure compensating dripper. For greenhouse or indoor growing the dripper should be a “CNL” device. CNL stands for “Compensating Non-Leak”.

“Compensating” means the dripper compensates for pressure variations within the supply line. That is, the dripper will produce the same precise drip rate regardless of the pressure in the supply line. For example, if you have a long row the pressure at the end of the line may be lower than the pressure at the beginning of the line which is closer to your pump. With Compensation, all drippers output the same flow rate even with these pressure differences.

“Non-Leak” means that the dripper only outputs water when supply line pressure is above 10 psi. When CNL emitters are used, all emitters in your irrigation zone turn on simultaneously when pressure is applied, then emit water at exactly the right drip rate. When pressure is removed, they all turn off simultaneously. If drippers without CNL are used, when water is initially turned on some drippers will flow and some will not as the supply tube fills with water. When the system is turned off, the entire volume of water in the supply tube will drain through the drippers at the lowest point on the row, overwatering those plants. CNL eliminates fill-up and drainage problems and is ideal for high frequency irrigation.

Which CNL Dripper does Grow Irrigation recommend?

The PC dripper you use is the heart of your drip irrigation system., so it is critical to use the highest quality dripper available. This is why Grow Irrigation only supplies Netafim drippers. Headquartered in Israel, Netafim is the largest and oldest drip irrigation company in the world, and has a global reputation for quality and innovation. When it comes to the dripper you will trust your plants to, only accept the best.

How do I connect the PCJ Dripper to my irrigation lateral?

The Netafim PCJ dripper has a 5 mm barb on one side, and either a 3 mm barb or a nipple on the other side. The 5 mm barb (barb that is part of the body of the dripper and not the cap) is the one that goes into the tubing. In the figure above, the 5 mm barb is the orange one. Simply make a hole in your tubing with a 3 mm punch (we sell several models), then push the 5 mm barb into the hole until it snaps in.

How do I bring the water to my plants?

In most applications, you will bring water from your dripper to your container using a length of Netafim SuperFlex 3 mm ID tubing. One end of the tubing connects to the dripper and the other end attaches to a stake which you place in your container. You can either have a single dripper connect to a single “Angle Barb” stake that goes into your container, or you can have a single dripper drive either two or four “Arrow Drippers” by using a manifold. Splitting flow with a manifold is often done to improve coverage by creating more than one drip point in a container, although some growers use manifolds to irrigate multiple containers with a single dripper. When using a manifold, it is important to terminate each piece of Superflex tubing with an Arrow Dripper, which balances the flow from each outlet by creating back pressure.

You can either build your own connection from the dripper to the container by assembling drip stakes, manifolds and tubing, or you can buy pre-made Dripper Assemblies which are ready to go as soon as they are plugged into a dripper.

Which dripper flow rate should I use?

Although there are many factors that affect this decision, by far the most common flow rate is ½ GPH (2 LPH) per drip point. When connecting a single dripper to a single Angle Barb stake you can accomplish this with a ½ GPH (2 LPH) Barb Outlet Netafim PCJ Dripper. If you are using a 2-way manifold to divert the dripper flow to two Arrow Drippers, use a 1 GPH (4 LPH) Netafim PCJ Dripper. If using a 4-way manifold and four Arrow Drippers, use a 2 GPH (8 LPH) Nipple Outlet Netafim PCJ Dripper. Note that all of the links in this paragraph take you to the page describing a bag of 100 drippers. For larger systems we also supply Netafim PCJ drippers in economical bags of 1000, with discounts for multiple bags.

What’s the difference between a “Nipple Outlet” and a “Barb Outlet”?

A Barb Outlet dripper has a 3 mm barb at its outlet end which connects directly to a piece of Netafim SuperFlex tubing. Use this when connecting a single dripper to a single drip point. A Nipple Outlet dripper connects to a manifold which can split flow into two or four pieces of tubing. It’s important to choose the right outlet for the application: a barb will not connect to a manifold, and a nipple will not connect to SuperFlex tubing.

How long should I run my system for?

The answer to this question depends on many factors including your container size, plant stage of maturity, media type and how often you plan to irrigate. As a starting point, run your system long enough to apply 25% of your container’s volume with each irrigation. For example, if you have two drip stakes in a 5-gallon container, each applying ½ GPH, you need to run your system long enough to apply 1.25 gallons which is 75 minutes. Make adjustments after seeing how well the root zone is wetted.

At what pressure should I run my system?

The PCJ dripper is designed to operate with an input pressure ranging from 10 to 60 PSI. Within this range, the output flow rate will be constant. We suggest running your system at 25 to 35 PSI which ensures all drippers stay within their operating range after accounting for line losses. Use a Senninger Pressure Regulator at the start of each zone to keep your supply pressure in tis range.

What is the filtration requirement for a Netafim PCJ dripper?

Generally speaking, the minimum filtration requirement for the Netafim PCJ is 120 mesh. A simple Screen Filter can be used if your water supply only has inorganic contaminants, usually the case with municipal or well water. If your water supply contains organic contaminants such as algae or certain organic fertilizers, a Disc filter or Sand Media filter should be used. Organic contaminants are usually present in surface water supplies such as ponds or canals.

What is a Drip Ring?

A Drip Ring is a new product type that works together with a CNL dripper to provide uniform coverage across an entire container. Drip Rings are quickly gaining traction in cannabis production because they provide uniform root zone coverage equivalent to spray stakes without wetting the plant's trunk or foliage. A Drip Ring is a plastic ring that sits on top of your media and encircles your plant, providing many drip points within each container. Connect a drip ring to a Netafim PCJ Barb Outlet dripper using a length of SuperFlex tubing to uniformly water your plant's entire root zone.

Grow Irrigation supplies the industry's two most popular drip ring products, the Netafim NetBow and the Primerus Pot-Dripper. Drip Rings are an alternative to manifolds and multiple Arrow Drippers for wetting an entire container.

What are high flow PCJ drippers for?

Grow Irrigation supplies ultra high flow Netafim PCJ drippers with 3.2 GPH (12 LPH), 6.6 GPH (25 LPH) and 10 GPH (40 LPH) flow rates. Most commonly, these drippers are used to supply spray stakes which produce a spray rather than a drip. This is required in some applications to ensure the entire container is uniformly wetted. Grow Irrigation carries Netafim PC Spray Stakes as well as the Primerus Spot-Spitter. Netafim PCJ ultra-high flow drippers can be used with either of these lines.

The ultra high flow PCJ drippers are also used in some very specialized applications, such as desert-grown date palms, where water needs to be applied quickly. Drippers used in these applications are often referred to as "bubblers".

Can I run fertilizer though my drippers?

Absolutely, as long as you use a high quality dripper such as the Netafim PCJ with good resistance to clogging. Accurate fertigation is one of the primary benefits of drip irrigation. Stick with liquid fertilizers that are formulated for drip irrigation, and always inject fertilizer upstream from your filter. When mixing fertilizers, first try mixing them offline in a jar (“jar test”) to see if they react with each other and create a precipitate. If this occurs, do not simultaneously inject them into your drip system – apply them one at a time with a clean water flush between applications.

Where can I get more information?

For more information, see our article Drip Accessories for Greenhouses and Indoor Growing. Also see the Netafim USA Plant Watering Systems Design Guide. And, of course, feel free to call us at (442)279-3152.