Drip Irrigation - Filters, valves and drippers!
Do strain yourself!
In the world of drip irrigation, tiny particles of dirt and debris are your worst enemy. This is because they can clog up your drip tubes and emitters, causing you to come home to dead or dying plants when you thought you had everything taken care of. To avoid this problem, a water filter of some type is required.
Filters come in a number of types and configurations, but for your purposes, you have two general categories to choose from. Which you choose depends upon your own water situation and how finicky you (and your plants) are about good clean water. The two types of filters are mesh and sediment filters. Mesh filters, one of which is illustrated opened up in the picture at left, are like a very fine grade of window screen. The size of the mesh openings determines what size particles will be stopped and what size will pass through. Drip irrigation kits usually include a mesh-type filter. The other type, the sediment filter, is most often used in whole house water filtration, but in my situation, I determined that I needed this level of filtration for my plants. Sediment filters consist of a housing and a cartridge, and it is the cartridge that does all the work. In my case, I decided on the finest carbon block cartridge I could find, which is a Matrikx +Pb1. This cartridge filters out particles down to 0.5 micron and even reduces some chemicals, such as lead and chlorine. With this cartridge, I can even feel safe drinking my well water if need be.
I'll take a moment here to describe my situation in a little more detail so you can understand why I chose such rigorous filtration for my drip system. In 2005, we experienced a few hurricane events, one of which was hurricane Katrina. She didn't pack much in the way of wind for us in south Florida, but what she lacked in wind she made up for in water. Incredible, copious amounts of rain left our house an island in the middle of a lake that was up to three feet deep. Although very little water got into the house, the water level was so high that, as the water subsided, it drained into my well at a high rate of flow. To my dismay, the high water also disintegrated some bags of nutrients in my garden shed, including a bag of micronutrients. While these are normally good for plants in small quantities, a 50-pound bag dissolving and then getting drawn down my well was not according to label recommendations! Shortly after, I began to see new leaves coming out distorted or discolored on my plants. It was at that time that I knew I needed to do something drastic to improve the water, so I obtained and installed a large whole house filtration unit at one of my main hose outlets coming from the well. I then made a mobile unit by mounting a 10-inch x 4 1/2-inch filter housing and cartridge on a heavy-duty two-wheeled Rapid Reel hose reel. This way, I could connect to any available faucet and obtain good filtered water for hand watering.
Once I decided on the drip system project, I knew I would need to have filtration, so I just added a housing/cartridge unit at each of the valve manifolds for my system. I chose the smaller 10-inch by 2 1/2-inch standard housing and cartridge combo for two of the manifolds and the larger 10-inch x 4 1/2-inch "big blue" units (see picture above, right) for the other two.
You will need to change your cartridge, or clean your mesh filter, periodically. Cartridges are rated for number of gallons they will treat, so you can figure your needs based on the number of drip emitters you have on the lines and the amount of time they are running. A simple example: if you have only one emitter that is rated for 1 gallon per hour (gph), and it runs for one hour each and every day of the week, that's 365 gallons per year, which means your cartridge will last a long time if it is rated for 5000 gallons. Of course, no one has just one emitter! If you have 10 emitters at 1 gph each running an hour every day, you'll need to change your filter cartridge in just under a year and a half. Cut your watering time down to a half-hour and your filter cartridge will last twice as long, provided that half-hour of watering every day is plenty for your plants. So you get the idea of how to figure the frequency at which you will change your filter cartridge. For mesh filters, I recommend checking and cleaning them once per week at a minimum, or more often if you find your water is rather dirty.
Opening and Closing
Once you have good water coming down the line, you need to be able to control how long the water flows. This is what the automatic valve does for you. My choice was the battery-operated type, which meant that I did not have to run electrical wiring out to the valves. It also meant that I'd have to program the zone time and duration at the valve rather than at a central controller or timer. These valves come in two basic types, which I'll call the electric ball valve and the electric solenoid valve (see solenoid type in thumbnail picture above). The solenoid type is also the standard type used in wired irrigation systems. The electric ball valve is a ball valve that is opened and closed by a small servomotor according to the time and schedule you input into the timer. These are less expensive than the solenoid type, which operate by an electromagnet moving a little plunger to release water pressure, which then allows a diaphragm to open and water to flow through. Water is stopped when the plunger moves back into position, increasing pressure on the diaphragm until the valve is sealed again. I have both types of valves in my system, mainly to see which of the two work the best for me. Of the two I'm using, the solenoid type takes one 9-volt battery and the ball valve type takes two AA batteries. So far, they both seem to work just fine.
A Drip is a Good Thing
Quite an array of options are available when considering drip emitters, which are the things that actually deliver water to your individual plants. My choice was the adjustable "shrubblers" on small plastic stakes (see picture at left for view of one in operation). These can be set to fully open, part open, or fully closed, according to need. They put out a spiderlike array of little water streams in a circle. You can get them in full 360 degree coverage or in 180 degree coverage. The latter is good for situations where you place the stake near the edge of a pot, as it will squirt the water just into the pot soil area, not into the pot wall. One emitter is good for 1-gallon to 3-gallon pots, but anything larger should have at least two emitters per pot. Large pots, such as 10-gallon and above, may be better served by a ring of emitter tubing. This 1/4-inch tubing has emitter holes spaced about 12 inches apart. You make an appropriately sized ring for your pot and connect with a 1/4 inch barbed tee connector, which is then connected via regular 1/4" tubing to your main water line. This main line is usually 1/2-inch black poly pipe. I'll cover basic and overall layout of a drip system in my next article.
While the drip emitters and drip rings will do fine for medium to large pots, what about your seedling trays and 4-inch or smaller pots? I set up an area just for these, assembling them all on benches, with the taller plants at the farthest point from the center of the setup. Then I installed mini-spinner sprinklers, or the lowest volume "wobbler" heads, on risers just tall enough (about 3 feet) to spray over the whole group. These can be included as part of one of your other zones, provided you do not have too many plants on the zone already. Also, be sure that the time you need for them to run is not too much for the other plants on the same zone.
Image credit: LariAnn Garner
Next: Tubing, fittings, and other accessories
Discussion about this article: