JARS v42n2 - Save Water Dollars-Use Micro Sprinklers

Save Water Dollars-Use Micro Sprinklers
E. White Smith
Tacoma, Washington

Sometimes important new things show up that we rhododendron lovers can put to good use. There are many different sprinkler systems available that do a good job of watering rhododendrons. Some sprinkler heads can cost many dollars and require a large pipe size and a large water meter or supply. Others are more economical. Recently I have changed my home yard over to "micro-sprinklers".

One of my first considerations was water cost. Many people think that we in the Pacific Northwest have very low water cost which is partially true. But, I am a park maintenance superintendent for the Metropolitan Park District of Tacoma. My crews take care of two thirds of the parks in the city of Tacoma. We have an annual water bill of over $70,000. Water does cost money for sure.

Another good reason I changed over to micro-sprinklers is that they will not only cut down on water use but will need a much smaller source of water. Water meters are also expensive. In the city of Tacoma we pay $5.50 per month on our water bill for a 5/8" meter. If we need more water we can have a 1 " meter installed. We will need to pay someone to do the work and then have an added cost of about $15 per month for the meter. Move up to a 2" meter and the monthly meter cost will go up to $50 - $60. We have one 10" water meter that cost us $850 per month plus the water we use.

Still another reason for using micro-sprinklers is to conserve water. Yes, we have a water shortage at times. As any area grows there is a lot of demand put onto the water distribution system. When these distribution systems need to be sized to handle extra needs the cost is very high. Some water companies put an 100% surcharge on their customers' bills to finance new water supplies and distribution systems. I like to think that my little bit of savings helps. If nothing else it should help my pocket book.

Sometimes water is harmful to our soils and plants. It is not all pure and good as we would like to think. Look at what is happening to the good farm soils in California. Micro-sprinklers put on very little water per setting.

I think it is a good idea to start the sprinklers running early in the spring and not let the root zone get dry. Then the small amount of water that the micro-sprinklers apply can keep the soil damp. I put aluminum pie tins under one of my micros and at 20 minute timings I did not get enough water to measure, but the root zone and the soil stayed nice and damp.

Water leaches plant nutrients down and away from the root zone. When we apply fertilizer it is not our normal objective to wash the plant food through the soil, but this is what happens with heavy watering. Nitrogen fertilizers are often very soluble and move through soils almost as fast as water. Even the so called "slow release" nitrogen will leach after it is released.

Micro-sprinklers can also add humidity on hot days and frost control in the early spring. You can easily water only where water is needed with micros and not waste water on the house, driveway, and so on, because you can place the sprinklers where you want water to be applied.

What You Will Need -
Automatic sprinkler systems have a few fixed costs that micro-sprinklers can help hold down. For an automatic system you will need some kind of timer or sprinkler clock. I use a six station, solid state, easy to program clock sold by the Rain Jet Company. This clock can be found for about $55.

You will also need one or more electric control valves that the clock can open and close. Electric valves cost from $12 to $35 for 3/4" sizes. Get the cheap ones and if they go bad replace them with new ones. Repairing electric valves is not hard but parts can be unavailable. With a micro-sprinkler system you will need fewer electric valves because these sprinklers operate at very low water pressure (20 to 30 pounds) and you can have many running on one line (up to as many as 70 sprinklers) at the same time.

The water pressure must be kept low. The sprinklers work best at low water pressures, so put many on a line or you might need to cut your pressure down another way. With micro-sprinkler systems you can use small pipe. You should not need any pipe larger than 3/4". Small pipe and fittings are much cheaper than larger ones. Small cheap pipe can lay on top of the ground whereas larger pipe is better buried. This costs money. If the small 3/4" pipe should get broken or freeze and break it is very cheap and easy to repair.

How much should parts cost? Electric clock = $55, electric valves = $12, 3/4" Class 125 PVC pipe + from $.45 to $2.00 per 10 foot length, PVC pipe fittings + $.11 to $1.50 each, sprinkler heads = $.85 to $1.50 each.

Where can you buy this equipment? Some suppliers advertise in the ARS Journal . You can write to them for information. Sprinkler clocks and electric valves can be found in the plumbing department of most hardware stores. I buy the pipe and parts at a local hardware outlet store.

How do you do it? Working with PVC plastic pipe is very easy. You can use poly pipe but PVC is much better. PVC pipe can be cut with a hack saw or any other fine toothed saw.

You will need to make a drawing of where you will want to run the pipe and where the sprinklers will go. The PVC fittings that you will need are 90 degree elbows, T's(tee's), maybe a + (cross) or two, some couplings, and some 3/4" slip x 1/2" inside thread bushings. Note that the sprinklers have 1/2" threads. You will need a coupling and a bushing for each sprinkler to glue onto the end of the 3/4" pipe.

Count the parts from the drawing and then buy at least ten more of each. Get lots of pipe. It is cheap and you will use a lot of pipe even for a small area. Get a pint can of PVC cement, clear, light bodied, fast cure. The PVC cement can should come with a round brush attached to the inside of the lid. You will also need some kind of adapter to join the 3/4" PVC pipe onto the main water supply.

Installing Your System -
First, hook up to the water supply. You should use some kind of back flow preventive unit to protect your house water if that is what you hook up to. You should have a plastic slip fitting that you can glue pipe into at the water source, so let's get started gluing!

Use the round brush from the glue can and coat the inside of the fitting first and then the end of the pipe. Push the pipe into the fitting, turning as you push. Hold it for a few (20 seconds) and then take a rag and wipe off the extra glue around the joint. A bead of PVC glue around the outside of a joint does no good at all and looks sloppy. Gluing PVC pipe is best done in cool weather. If it is very hot outside the glue will dry too fast and you will have trouble making the connections. If it is very cold the glue will dry too slowly. The pipe and fittings must be dry for gluing. You can not do this job when it is raining.

Run the pipe along the ground to where you want a sprinkler or a turn location. Put an electric control valve in to control the line that you are working on. Putting all of the electric valves into a manifold or valve box at one location will make things simpler in the long run.

You will probably need to cut the pipe at this spot. After cutting there will be a rough edge on the inside of the pipe that you must remove. A small knife works well, but I use my fingernail to remove the rough stuff. Try very hard to keep dirt and pipe filings out of the pipe. We want nice clean pipe so that we do not plug up the small sprinkler heads with debris.

If you are putting a sprinkler at this location, you will need to cut a riser to hold the sprinkler above the plants. The reason we are using 3/4" PVC pipe instead of 1/2" is that the 3/4" will stand upright by itself.

As you lay pipe you will need rocks, bricks, small logs or something like that to hold the pipe in place. You will also be able to put some of the pipe under ground where it crosses paths or is in the way. Just scratch a trench and put something on top to hold it down.

The PVC pipe is white colored, which may not look good. I painted the pipe with black spray paint where it showed too much. A bark or sawdust mulch will cover and hide the pipe nicely.

Run the pipe out and put the micro-sprinklers only where you need watering done. The sprinklers can be 15 to 20 feet apart. You can go up over structures, hang the pipe from the top of a lath house, or hook it onto a fence to get to where you will need sprinklers. This pipe is very easy to work with because it will bend quite a bit. If you make a mistake it is easy to cut a piece out and change the layout.

Some things to remember: automatic watering systems are NOT really "automatic", they need to be watched and adjusted at times; you might need to do some supplemental watering, but for the most part the micro-sprinklers will do a good job.

This system is easy to install and will save you water and money in the long run. You could be involved in the wave (spray) of the future.

E. White Smith, District #3 Director, read Jean Minch's article in the ARS Journal , Vol.41:2 (Spring 1987), and decided to install his own micro-sprinkler system. E. White Smith is the coordinator of the "Vireya Vine" newsletter for the Rhododendron Species Foundation.