I found a good liquid repellant, that does a fair job, whose primary ingredient is garlic. Aside from smelling somewhat like an Italian eatery it does work well for a few days at a time, but distribution can take a while. Using a hand feeder attached to my garden hose to spray the mixture is slow if I want to ensure the yard is covered.
Then I saw that my lawn sprinklers cover the entire place, quickly, and decided to attempt running the mixture through them. I've seen systems online sold for $1400+. I did mine for less than $30.
The idea was to steal the water from my backflow preventer, route it through the "venturi" feeder to collect the garlic mixture, and then join back up with the original outbound line to the sprinkler zones. I had to be able to shut this off and on, both to water my lawn as well as purge the mixture from the lines which only takes a few minutes. I started with this assembly which came with the house. There is a black sprinkler head in front which unfortunately is in the way of the lower ball valve in the photos, but the fence turns and this angle was the best I could do.
Unlike some feeders which use a straw to collect the mixture, this one has two orifices of different sizes: the smaller one is used to fill and pressurize the reservoir; the larger one is the "venturi" orifice to pull the mixture out.
Once the reservoir is filled the output lists as 3 tbsp per gallon of water. I'm currently testing the zones to see what the rates of depletion are.
Step 1: Parts & Tools
(3) 1" PVC ball vales;
(2) 1" PVC elbows (90s)
(2) 1" PVC T-fittings (slip). I used one with a side-out as I had to turn a corner close to my fence line.
(1) 5ft length of 1" PVC (sched 40). I had quite a bit left over.
(2) Hose adapters: 3/4" threaded to 1" PVC (need male & female threads)
(1) brick or block of wood.
(1) 3" PVC coupler
(1) 3" PVC to 1" adapter
(1) 3" threaded PVC cap
(1) 1 1/2 " to 1" PVC Wye adapter
The last four items were swapped in place of the plastic feeder from the earlier version. That is the blurred portion of the image.
Channel lock pliers
Step 2: Assembly
Just before the pipe enters the grass, I put another t-fitting in the line a few inches above the ground. Halfway in between I put one of the three ball valves. Step 4 has the ordering of the valves for use.
The Wye sits in the bottom with the 3" stack sitting on top of it. I put a fiberglass bottom to it with a 1/16" orifice drilled in the center to meter out the mixture. The flow in the 1" pipe, along with the drip, seems to make for a good mixture. I'll adjust it as I take more measurements.
There is enough room, when installed, to unscrew the cap on top and fill the reservoir with the mixture.
Step 3: How to Use:
1. shut off one of the preventer's valves before using the ball valves we added; I find them to be a little tougher to turn and would rather not have the pressure on them;
2. Open the top ball valve;
3. Close the middle (vertical) ball valve; and
4. Open the bottom ball valve.
5. open the preventer's valve to start the flow of water. The water now routes through our new piping and re-enters the line to the ground (and zones).
To stop using the feeder, repeat step #1, reverse steps (2,3, and 4), then repeat step #5 (re-opening the preventer's valve to start the flow of water). Water is routed as before.
I don't know the lifespan of the feeder from the hardware store, but the orifice could be duplicated, and I'll add a method of building a stronger "venturi" mixer solely out of PVC when that time comes.
I plan on building a small 3-sided box from cedar pickets to disguise it.
I also recommend running the system for a few minutes on water after spraying to purge the lines. The mixture I use has no particulate matter, but it's nice to clean it out.
Step 4: Updated: 6/28/13
1. I added a 3" PVC section with a female threaded coupler (and threaded cap for it) as well as a 3" to 1 1/2" fitting at the bottom.
2. Because it was a bit taller than desired I "moved" it out of the way by putting two 90 elbows on a t-fitting where the first reservoir was. This created a new problem: tightening the threaded cap so as to prevent leakage when in use.
3. between the reservoir's t-ffiting where it meets the main line, and the downline into the ground, I added a t-fitting with a simple brass spigot. With the water to the sprayer shut off you can open this to drain the chamber and make room for your solutions.
4. I also created a pressure-plug type of fitting inside the top cap to prevent leakage during use. I took the idea from pressurized aircraft which use the interior cabin pressure to actually hold the door shut. This works very well as the water pressure actually makes the seal tighter for you. A wingnut on the outside is there to hand tighten and get it seated before pressurization and to prevent dropping it in the chamber when re-filling.
5. under the cap is a 1/2" x 6" carriage bolt with some oversized washers and rubber washers. Epoxied together, they are simply tightened with finger pressure by the wingnut on top until water pressure takes over.
6. i have widened the hole with a 1" hole saw to give more room to pour in my solution.
I've included some new photos that will explain this much better.