Drip Assemblies and Accessories for Greenhouses and Indoor Growing
We often get questions about the array of products available to connect drippers such as the Netafim PCJ to containers. Flat Manifolds, Stackable Manifolds, Arrow Drippers, Angle Barbs, Weights and Assemblies are all options, and choosing the right ones will precisely deliver water to your plants. However, not all of the products work together – for example barb-outlet drippers do not work with manifolds or multi-outlet assemblies – therefore it is important to make the right choices.
Anatomy of a Greenhouse Drip System
In most greenhouse drip systems, drippers at individual containers are supplied by ½” or ¾” diameter PE Supply Tubing running along each row. Drippers are punched directly into the Supply Tubing, then water is brought from each dripper to a container through a length of 1/8” diameter Super-Flex Tubing. The other end of the tube connects to a drip stake that is inserted into the soil to hold it in place.
There are many variations on this basic concept. Each dripper can attach to a single drip stake which supplies a single container, or 2-way and 4-way manifolds can allow each dripper to supply two, four or even more drip stakes. Each drip stake can supply a single container, or multiple stakes can be placed in larger containers. Each combination determines the specific components that are used (barb outlet or nipple outlet dripper, Arrow or Angle Barb drip stake, type of manifold, etc.), so it is important to read this article to be sure you select the right components for your application.
CNL Drippers: The Heart of Your Drip System
“Compensating” means that it 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, as long as it remains between 15 and 60 psi. 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 water supply. 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.
Nipple-Outlet vs. Barb-Outlet Emitters
Netafim PCJ Drippers are available with two outlet styles: nipple or barb. It is important to choose the right one for your system because the two connections are not compatible.
Barb-Outlet (left) and Nipple-Outlet (right) Drippers
A barb outlet connects directly to a piece of 1/8” Super Flex tubing. The most common application for barb outlet drippers in greenhouses to irrigate a single plant with each dripper by connecting tubing directly to a ½ GPH barb outlet PCJ Dripper on one end, and to either a Angle Barb drip stake or a Slimline Easy-Close Weight on the other. Barb outlet drippers should not be used with Manifolds or Drip Assemblies – these require nipple-outlet drippers.
A nipple-outlet emitter connects to a manifold or a fitting such as a 1/8” elbow. Nipple outlet drippers also connect Netafim Drip Assemblies. A typical application for a nipple outlet dripper would be to connect a 2 GPH nipple-outlet PCJ dripper directly to a Flat 4-Way Flat Manifold, then connect four 24” lengths of Super Flex tubing to the manifold outlets. The other end of each length of tubing connects to an Arrow dripper. This configuration can be used to irrigate four containers with a single dripper, each at a rate of ½ GPH. The same thing can be achieved with a 24” 4-way Assembly.
Summary: Use a barb-outlet dripper to directly connect a dripper to a piece of 1/8” tubing. Use a nipple-outlet dripper to connect to a Drip Assembly, Drip Manifold or Drip Connector.
Arrow Drippers vs. Angle Barb Stakes
An Angle Barb Drip Stake is a simple device that holds the end of a piece of 1/8” tubing in place in your container. If you wish to irrigate your container with a single PCJ Dripper, you can connect the Dripper to the Angle Barb using a length of Super-Flex Tubing, place the Angle Barb in your container and you’re ready to irrigate.
An Arrow Dripper is a drip stake which creates back pressure. This is important when a single dripper supplies more than one container. Without back pressure, the flow from the dripper may not be evenly divided between the containers. For example, if a single dripper supplies two containers without back pressure devices, and each container uses a different length of 1/8” tubing, the stake with the shortest length of tubing will get the highest flow rate. The Arrow Dripper evens this out. The nominal flow rate for an Arrow Dripper is 1/2 GPH, however it will work for lower flow rates as well. For example, a 1 GPH nipple-outlet dripper connected through a manifold to four Arrow Drippers will deliver ¼ GPH to each container.
The accompanying figure shows the Arrow Dripper to the left and Angle Barb to the right. While the Angle Barb holds tubing with a simple barb, the Arrow Dripper shows a more complex tubing insert which includes a tortuous flow path to create back pressure.
Summary: Use an Angle Barb Drip Stake to connect a single dripper to a single container. Use an Arrow Dripper when using a single dripper to irrigate multiple points, for example when using manifolds or multi-outlet drip assemblies.
Non-Stackable vs. Stackable Manifolds (or Assemblies)
A Non-Stackable Flat Manifold is a simple fitting that connects a single nipple-outlet dripper to more than one length of Super-Flex Tubing. Grow Irrigation supplies both 2-Way and 4-Way Manifolds. A Non-Stackable Assembly is based on a non-stackable manifold, and contains all of the parts needed to irrigate more than one container with a single nipple-outlet dripper. Grow Irrigation supplies both 2-Way and 4-Way Assemblies.
A Stackable Flat Manifold connects a single nipple-outlet dripper to four lengths of Super-Flex Tubing and to an additional manifold. The second manifold can be stackable or non-stackable. The last manifold to be connected must be non-stackable in order to stop flow at the end. For example, a 4-way stackable manifold can be connected to a 2 GPH nipple outlet PCJ Dripper, a second 4-way stackable manifold can be attached to the first, the a 2-way non-stackable manifold can be attached to the second 4-way. The result is ten connections to a single dripper at 2 GPH each. As noted above, Arrow Drippers must be attached to the other end of each length of Super-Flex tubing to ensure all containers connected to the dripper receive the same amount of water.
Summary: Use a Non-Stackable Flat Manifold or Assembly to connect a nipple-outlet dripper to two or four connectors. Use a Stackable Manifold or Assembly to combine manifolds for more connections. The last manifold should in the combination should be Non-Stackable.
SlimLine EZ-Close White Weights (and Assemblies)
The EZ-Close Weight is used to hold the end of a length of Super-Flex tubing in a small container. The most common use is for hanging baskets. In addition to holding the tube in the right place, it also has a shutoff feature which allows flow to an individual container to be stopped when not needed. Grow Irrigation also supplies 24” Weight Assemblies and 36” Weight Assemblies which include a single ½ GPH barb-outlet dripper, a length of Super-Flex Tubing and a single EZ-Close weight.
Summary: Use SlimLine EZ-Close White Weights and Assemblies to irrigate hanging baskets from overhead supply lines.