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Drip Irrigation on the Balcony

Most vegetable plants thrive with a continuous supply of moisture during most of their life cycle. But typical container plants watered by hand receive a days worth of water in a matter of minutes. Over the course of the day this water gets used up by the plant, evaporates off the soil surface or drains out the bottom of the container. So for part of the day, the plant is over watered and for the rest of the day, the plant is dry and the roots vulnerable.

Ideally you want to have a system for watering your plants that does it perfectly every time, consistently, with little effort. You want to provide deep watering but not all in one blast. I've always thought self watering containers were the best way to get an even flow of moisture to your plants when they need it without over watering. And with the right container, it's almost fool proof. But I've also played around with another alternative which is drip irrigation.

Drip or low-flow irrigation, also know as micro irrigation, is a watering system designed to provide just the right amount of water to your plants right where they need it. In a garden, watering usually means a hose and nozzle and lots of water is wasted in areas where the plants don't need it. Drip irrigation delivers water right to the roots of the plant. And it does so in a slow constant drip that provides the plant with a gentle but continuous supply of moisture. Once the system has been established, all you have to do is turn on the water supply and let your irrigation system take care of watering your plants.

Watering plants on my balcony is time consuming and the biggest problem is subjecting my non-self watering container grown plants to constant dry-wet cycles. A drip irrigation system would help me smooth out this watering cycle and take a big part of the effort out of watering my plants. But can this been done effectively on a balcony?

On my balcony, my drip irrigation options are limited to gravity fed and therefor, low flow irrigation methods. There are no sources of pressurized water. No faucet is available. And not that it really matters but there are no electrical outlets either. So any system I come up with has to use gravity to distribute water. Pop up sprinklers and sprayers aren't going to work. I have seen IV bag style drippers available that are nothing more than a large bladder for storing water that is held above the plant, and leaving the bottom of the bladder is a long flexible tube that is pinched off somewhere to limit water flow. All you have to do is play with the flow rate to get the drip rate where you want it and keep the bladder full. But I need something bigger. Something that can hold more than a gallon of water.

I have seen kits available for turning rain barrels into water reservoirs for drip irrigation systems. I don't have a rain barrel but a tote or 5 gallon bucket is easy to come by and keep filled. Here is a list of parts I used for my initial project:

• A 5 gallon bucket to use as a reservoir
• A brass 3/4 inch boiler drain faucet
• Pair of 3/4 inch nylon conduit nuts
• Pair of 3/4 inch rubber gaskets
• 3/4 inch to 1/4 inch hose adapter
• low flow drip irrigation drip spikes
• 1/4 inch T connectors
• A good length of 1/4 inch plastic water line

In the bucket I cut a 3/4 inch hole to fit the brass drain faucet and I used a pair of 3/4 inch nylon electrical conduit nuts with some home-made rubber gaskets to hold and seal it in place. With this up on a table, I had a temporary source of water for my plants that I could control.

I picked up a hose adapter that mates 1/4 inch flexible tubing to the faucet on the bucket and a number of plastic barbed T connectors to branch this line to drip points placed in a couple of test containers. All I had to do is turn on the water and watch it flow to all my drip points. And with the valve I was able to control the overall flow rate if necessary.

Of course, in practice things never work exactly as planned. One problem with this system is that the different points along the tube will experience different flow rates depending on distance from the source as well as bends and kinks in the supply tube. Some drippers drip profusely and others hardly at all. The problem with the drip spikes is that they need to have a source of water with more pressure than I am providing. These are plastic spikes that insert into the soil and at the top on one side is a 1/4 inch hose connector and a little drip outlet for water output on the other side. You typically need at least one per plant. They are designed to limit the flow to 1 or 2 gallons/hour. With more pressure from the supply I would have been able to maintain consistent drip rates across the entire system.

To do this properly, I should have used a larger diameter supply line: 1/2 inch instead of 1/4 inch. This would allow for much greater flow through the system to the branch lines and drippers. There is just too much resistance in the 1/4 line. I should also use a much larger reservoir. A tote perhaps, with at least 10 gallon capacity. When full, this would provide a bit more water pressure. Perhaps with a little more water pressure and a larger supply line, the drippers might work a bit better.

Something else to consider is that as the water level in your reservoir drops, so will the water pressure coming out of the faucet. The higher you sit your reservoir above you system, the higher the water pressure coming out of it will be.

Something else I played with was the use of a hose faucet timer. This is a device that would normally be used between an outdoor faucet and a garden hose... or a drip irrigation system. You can get these at any garden center. They provide a number of options for having the water turn on and off at preset times. I thought this would be great for days when I can't water the plants but I failed to realize that all of these devices require a high pressure water source to work. This particular unit requires at least 10 psi. With my little gravity fed system I get no where near that amount of pressure and with the timer value open I get only a drip through the device.

Another way to accomplish drip irrigation on a small scale is with individual feeder tubes siphoning water from a bucket or tote. Forget the faucet and fancy drip irrigation parts and just use a bucket or tote with some lengths of flexible aquarium air line tubing. With the water source on a table or bench above the plants, and the tubing inserted into the bucket, suck water out through the tubes and if you keep the drip ends below the ends that are in the bucket, water will flow continuously out the tubing. As long as you keep water in the bucket and the ends of the tubing in the bucket under water, this will continue to work indefinitely. You can pinch off the tubes to limit the water flow to a drip or use aquarium air valves to provide more accurate control of the water flow.

The only problem I have with these low flow, gravity fed drip systems (in general) is that there is a fair bit of fiddling around to get the flow rates right. If the drip rate is too low you will only moisten part of the soil in the container. And too fast just drains the reservoir with water leaving the containers out the drain holes. For me, without a pressurized and continuous source of water, it just seems like too much effort. Still, I will likely make some modifications and try again next season. If I can come up with a proper timer and valve combo to automatically turn the system on and off, I would likely do away with the drippers and just feed water directly into the reservoirs of my self watering containers and use the system to top them up while I'm away.