If you’ve decided to put in irrigation for your garden there are quite a few things you will need. Some are obvious like a water source, irrigation line, etc. However, the trick is figuring out what types of things do you need? Well a lot of it depends on the type of irrigation you are using. Because we focus on vegetable gardening on this blog, we’re also going to focus on the best way to water a vegetable garden. Most likely you will want to you use drip. There are several different types of drip line and they all have their benefits and disadvantages.
1. Piping & Tubing:There are several types of piping and tubing. The most popular piping is the white PVC hard pipe. This pipe is for underground use. UV rays from the sun will break it down so it’s not recommended to be above ground. I usually specify Schedule 40 (SCH 40) pipe, which denotes the wall thickness. It’s the standard pipe you can find at just about any hardware store. It does come in different sizes, 1/2″ being the smallest. Tomorrow I’ll go over how to size your pipe if you do decide to use it. Risers that come out of the ground off of the buried pipe are usually gray. They contain carbon in them to help keep them from degrading.
There are different types of connectors. Some connectors are threaded. When putting together threaded connectors always wrap teflon plumbers tape three times in the direction of the threads. This helps lubricate and seal the connection. For slip joints you want to use a primer and chemical solvent or pipe cement. Primer is very important for any lines that will hold pressure. There is a solvent you can use that doesn’t need primer called Christy’s Red Hot Blue Glue. Techinically it’s not a glue, but it’s a catchy name.
|1/2″ Poly Tubing|
There is also 1/2″ and 1/4″ poly tubing. This is a flexible black tubing that comes in rolls. This should be used above ground (but it can be hidden under mulch). This you will generally use to reach plants. Barbed connectors are put into this using a punch specifically designed for this tubing. This can be either pressure compensating drippers (see #2) or double barbed connectors. The double barbed connectors connect 1/4″ tubing into the 1/2″ tubing. There are also T Connectors, Elbow connectors, and Compression Couplers to help you design your irrigation system.
Three additional types of tubing are soaker hose tubing, T-Tape and emitter tubing. Soaker hose is a porous flexible black tubing that drips water over it’s entire length. It’s not recommended if you have hard water though, as the pores can easily get clogged. T-Tape is a flat hose that has slits on the bottom at specified intervals. When water enters the tape it expands into a tube, a flap on the underside opens up and the slits drip water. This one is good for long, straight runs. It cannot be used on curves though. It is also the least expensive of most drip systems and what we use in our garden. Emitter tubing, which is by far the most expensive, contains inline emitters at specified intervals. The soaker hose and emitter tubing can be connected to 1/2″ poly tubing with compression fittings (for 1/2″ lines) or barbedconnectors (for 1/4″ lines). T-tape requires it’s own specific fittings to connect to poly tubing.
It’s also important to note that fittings from one manufacturer of tubing won’t necessarily fit other manufacturer’s tubing. For example, we purchased 1/2″ tubing from an online farm supply store. It turns out that the outside diameter is greater than 1/2″ so the fittings at the hardware store don’t fit it, which are the most convienent fittings for us to purchase.
2. Drip Emitters: These are usually little button drippers. They have pressure compensating drippers (note that one end is barbed and one is smooth) that can be inserted right into 1/2″ poly tubing and will drip at a given rate – usually 1/2 - 2 GPH. There are also in-line drippers that have two barbed ends. These must be inserted into 1/4″ poly tubing. There are also what’s called bubblers that can be inserted into 1/2″ poly tubing. These release a lot more water and need a lot more pressure to work well so you cannot run a long line of them. I only use bubblers on my fruit trees, which need more water than a normal drip emitter can supply.
3. Controller Valves & Associated Accessories: The controller and valves are the most important part of an irrigation system. These are what controls the water in your garden. You can go with a simple pneumatic controller with a hand turned compression valve, or you can get fancy with a 6 station automatic controller with automatic valves. We used the simple version last year but are currently converting our system for the fancier version.
A pneumatic controller is similar to a kitchen timer. You just turn the dial to the time you want the irrigation to run. When time runs out it shuts off. You use it with the compression valves, which you have to turn by hand for what beds you want to run. With this type of set up you have to be available.
The best, and of course, most expensive controllers on the market are the “Smart” controllers. They are usually synced to either your own small, personal “weather station” or a satellite which tells it the precipitation, and evapotranspiration of your plants for the current weather and then runs accordingly. This type usually requires a monthly or yearly subscription.
The automatic controller has days and hours in it so you can program it to go on certain days for a given time. A “set it and forget it” type of controller. This controller operates the valves to turn on and off. There are also battery operated valves that are a similar idea. However, I don’t recommend these because they are not reliable. If a battery dies while you’re on vacation it can either leave the valve closed and not water anything at all, which is critical during the summer, or it can leave the valve open wasting hundreds of dollars in water and possibly killing plants. The hard-wired controller is usually located in a garage. It’s wired into the building’s electrical. It then has low voltage outdoor rated wiring that runs to the valves to control them.Where wires are spliced together, make sure to use grease caps to protect the wires from water.
Along with the valves, there are some accessories you must include. First is a back flow preventer or anti-siphon device. These keep irrigation water from being pulled back into potable drinking lines and contaminating the water supply. They are required on all irrigation systems. A lot of valves already come with the anti-siphon, just double check this. You will also need a filter to remove any debris or deposits. This will save your emitters or hoses from getting clogged. Additionally you will want to have a pressure regulator. The common household water pressure is around 50 psi. Drip irrigation needs 10 psi to run optimally. Higher pressures will blow out the emitters or hoses.
Tomorrow I’ll cover how to size pipe and possible ways to lay out your irrigation in vegetable beds.