Spot Spitters for Irrigation

At Midori Bonsai Club's General Meeting on October 7th, Joel Miller explained the the benefits of using "spot spitters" for automating the process of watering bonsai, pre-bonsai and container stock, and discussed the benefits and the technical points affecting their use in container gardening.

Joel explained that the manufacturer's specifications concerning water flow and calculating the lengths and diameter of the major distribution lines is critical in ensuring enough flow for adequate coverage.

He also provided a live demonstration of spot irrigation at work.  In the right frame you can see a piece of supply tubing to which a green emitter stake has been attached. Unlike conventional drip irrigation, which relies on extremely low flow rates and is prone to clogging, the Spot Spitter uses a higher flow in a very economical design that distributes water over a wider area. The stakes themselves are very inexpensive.

The components at left show how a water connection can be made to an existing hose or sprinkler system.  The water supply enters at left, passes through a ball valve, a filter, a pressure regulator and a compression fitting that adapts the hose threads to 1/2", 3/4" or 1" diameter poly tubing.

Joel pointed out that for a system of any size, supply lines of at least 3/4" are recommended in order to get enough flow.

He provided the following USE AND INSTALLATION TIPS and SPOT SPITTER STARTER KIT as a guide.

SPOT SPITTER USE AND INSTALLATION TIPS

by Joel Miller

If there seems to be interest in this method, I will publish an article in the newsletter with a more detailed explanation.

DESIGN & INSTALLATION

• Don't use 1/2 poly lines unless you just have a few trees on one or two benches. Over-design the system to provide capacity for future growth.
• Use 3/4" poly lines (or even 1") if you can. The downside is that the compression fittings are not available easily.  However, I have these parts.  I use 1" lines in my system.
• Don't restrict the water source. Only use a hose bib for a very small system  Otherwise make a direct connection to at least a 3/4" pipe.
• If you use a hose to connect your system, you must use a high quality rubber 3/4" hose.  They are available at Home Depot (50' of 3/4" rubber hose is about $26.)
• 1" dia. in-line electric valves don't cost any more than 3/4" valves, so use 1" valves.
• If you are planning a big system and are unsure of how to calculate flow rates, you may wish to contact Joel for assistance.
• Ignore the 5' limitation Roberts states for the 1/8" tubing. I've gone more than 10' with a 20 psi regulator. It's more important that your tubes are out of the way - it's easy to inadvertently kick them out.
• If you plan to use the system to water valuable trees while you are away, consider a completely redundant system. That means two timers connected to different circuit breakers, and two independent sets of tubes and spitters connected to different water sources.

USING THE SYSTEM

• If you have been hand watering, you have probably been doing so only once a day.  Think about customizing your watering schedule with two (or more) sprays a day so your trees have a more stable moisture level.
• Check your system regularly, particularly in hot weather. It's a natural tendency to assume automatic systems are working and just forget about them. With spot spitters, you can have an overlooked dry spot, or may have accidentally pulled out a line with your foot. Or, the entire system could have failed.
• If you don't see the area that you are watering every day, consider routing a length of 1/2" poly tube to a place you do look at every day.  Put a spitter on it and you'll see if your system is working.
• If you have hard water, remove the spitters each spring and soak them in vinegar, which contains acetic acid that will dissolve the calcium deposits.
• Spot spitters are an ideal way to fertilize. I use a Dosatron and I never need to worry about fertilizer.  A constant low-dose application of fertilizer works better than a periodic dose.

SPOT SPITTER STARTER KIT

(Cost is approximately $150)

(1) Female Hose thread to Female Pipe Thread adapter

(1) Filter

(1) 20 PSI Regulator

(1) 1" Electrical Valve

(2) 1" to 3/4" Bushings

(1) Teflon tape

(1) Manifold for three 1/2" Poly tube Lines

(3) 1/2" MPT-to-poly adapters

TUBING

(1) 100' roll of 1/2" poly tubing

(1) 1000' roll of Roberts 1/8" poly tubing

(1) Roberts hole punch

SPITTERS

(25) Light green low-flow 160-degree spot spitters (18 per 1/2" lateral at 20 PSI)

(25) Brown low-flow 90-degree spot spitters (18 per 1/2" lateral at 20 PSI)

(50) Orange Mini Flow 160-degree spot spitters (30 per 1/2" lateral at 20 PSI)

(50) Gray Mini Flow 90-degree spot spitters (42 per 1/2" lateral at 20 PSI)

The links above to Morton's Horticultural Products is for your reference only. We have had no business relationship with them.