Watering the Urban Forest - Page 2

By Ed "Redwood" Ring

Materials Required

The EcoWorld approach to watering trees in urban and semi-urban groves, relies on using half-inch flexible plastic pipe to reach trees even when they are several hundred feet away from the valve. At a minimun, here is what is required for a manually operated system that can potentially be designed to water several hundred trees on .1 to 10 acres:

Water Source:

In a semi-urban setting, a well is often the water source. Output is typically measured in gallons per minute. If you have a lot of trees over an area of 3-5 acres, with, say, terrain that changes altitude by 50 feet or more up or down from the source, you'll need to be able to produce 10+ gallons per minutes with your well. If you only have vertical changes of 20 feet or less, and your site covers 1-2 acres, you probably can get by with 5 gallons per minute from your well.

(a) 1/2" Flexible Plastic Pipe  (Don't use ANY 1/4" pipe!):

1/2" Flexible Plastic Pipe

This pipe is ideal for watering groves of new trees in areas from .1 to 10 acres, as long as there's adequate water pressure going in. Damage from squirrels and other critters is unusual with 1/2" pipe, whereas you should avoid 1/4" pipe altogether. Not only does 1/4" pipe get frequently munched by squirrels, but it tends to clog with sediment much sooner than 1/2". Using 1/4" flexible pipe is also a waste of time and more costly, in that it requires more materials and more steps to achieve the same results as can be achieved with 1/2" pipe.

Cost: 500' rolls can be had for around $30.

All other components that connect to the 1/2" Flexible Plastic Pipe (from source to end):

Cost: Most adaptors cost no more than about a dollar each, often much less. Emitters come in quantities of 10-100 and can be had for about $.20 each in larger quantities.

(b) At the source (Upstream): 3/4" Hose to 1/2" Pipe Connector:

3/4" Hose to 1/2" Pipe Connector

Assume you have a hose faucet, called hose bib, or hose spigot. These are typically 3/4" in external diameter and "male" threaded at the end where the water comes out. Your connector is about 3 inches long, and is usually made of black plastic. It has a female hose threaded input on one end that screws onto the hose bib. On the other side of the connector is a 1/2" diameter hole ringed with hard plastic that is slanted inwards. To hook the connector to the pipe, the 1/2" pipe is simply pushed into this hole about one inch. Because the rim of the hole slants inwards, the pipe goes in much easier than it comes out, making for a seal that can withstand up to 20 PSI or more.

(c) At the source (Upstream): 15 PSI Flow Restrictor:

15 PSI Flow Restrictor

This adaptor will prevent too much pressure from coming into your system. Pressure balancing is important but should not be over-complicated. Make sure you don't blow out your connectors and emitters with too much pressure, and on the other hand, be sure adequate water pressure is getting to all the emitters, especially those who are at points uphill from the source, or at the far extremities of the system. Refering to EcoWorld's water flow-rate worksheet can help you figure out how to fine-tune your pressure, but turning on the faucet a little at a time as you test your system can work fine to gage and adjust water supply vs. water emissions. On large systems a flow restrictor isn't usually necessary, and on small systems, you may want to actually buy a pressure regulator, which is a flow restrictor that connects to a hose spigot with a hose spigot output, but includes a pressure gage and a flow-rate adjustment knob. These cost about $25, whereas the standard 15 PSI Flow Restrictor only costs a couple of dollars.

(d) Along the pipeline: 1/2" "T" Connector:

1/2" "T" Connector

This will allow you to split one line into two. You may choose, of course, any one of the three openings in this "T" shaped adaptor to be the one into which you press the 1/2" hose that is to be your water source. The remaining two holes can then be used to deliver water from one source to two destinations. You can do this throughout your grove, to bring water to every tree with what hopefully is the most efficient use of pipeline footage and connector junctions.

(e) Along the pipeline: 1/2" Extension:

1/2" Extension

If you run out of 1/2" pipe, for whatever reason, and need to extend the line, this adaptor, has the typical inward slanting "one way" holes that you press the 1/2" pipe into. This approximately 3" long adaptor extends your pipeline in a straight line, of course. If you are operating around structures, you may need the 1/2" "Corner" adaptor, which extends your pipe while also making a 90 degree right angle with the pipe.

(f) Along the pipeline: 1/2" Shutoff Valve:

1/2" Shutoff Valve

Sometimes trees in the grove need to get a little less water, or a little more. Shut-off valves, placed strategically along your pipeline's many forks, allow you to manually fine-tune your watering. If you have to add or repair a section, a shut-off valve can take that section off line while the rest of your system operates normally. Just make sure you don't leave some area shut off that you meant to turn back on!

(g) Where the pipeline passes a tree: 1/4" Emitters:

1/4" Emitters

Getting water to the trees depends on poking an emitters into the 1/2" pipe at a spot along the pipe where it passes close to each tree. The emitters are about the size of a fresh red grape, maybe 3/4" in diameter. The mid-section is shaped like a thick coin, this is the flow-restrictor. Out one end is a 1/4" diameter, 1/4" long "dripper" output. Out the other end protrudes a similar proportioned, but arrow shaped barb, that has a hole in the point to admit water from the 1/2" pipe. There are special tools to poke a hole in the 1/2" pipe that the emitter barb is then pressed into till the wider back edges of the arrow or barb are all the way inside the pipe, making a tight seal. If you don't have these special tools, or even if you do, a properly applied ice pick or awl makes a hole in the pipe just as well or better. Just be sure you don't accidentally poke the much sharper awl out the other side of the 1/2" pipe. Emitters usually come with three flow rates, (1) 1/2 gallon per hour, (2) 1 gallon per hour, and (3) 2 gallons per hour. With the popular "Raindrip" brand, one side of the "coin" shaped midsection of the emitter is colored to indicate that emitter's gallon per hour flow rate; red = 1/2, black = 1, and green = 2. You should try to anchor your pipeline's emitters by the trees to make sure they don't slide away from where the water needs to go. There are special stakes for this or you can improvise with sticks and nursery tape.

(h) At the end of the pipeline (Downstream): 1/2" Hose End Clamps:

1/2" Hose End Clamps

These consist of two hard plastic 1/2" long cylinders, or rings, placed side by side to look like an 8, with internal diameters of 1/2" inside each cylinder. The end of the 1/2" pipe is pushed through one of the cylinders, bent over and then pushed back through the adjoining cylinder from the other direction. This creates a seal where the pipe has been bent completely over, which is held in place by the rings of the clamp. Be sure to unhook your end clamps by sliding the clamp upwards on the pipe (upstream) to allow the end of the pipe to come out of its ring so the pipe can be temporarily restraightened. You need to periodically unhook these and let the water run out at full force to bleed sediment out of the pipeline at the lower elevations, and bleed sediment as well as air pockets out of the pipeline at the higher elevations.