DIY Pest Control Through Lawn Sprinkler System




I live in Texas which means we have only a few months out of the year without mosquitoes.  My wife and I don't like the toxic products as we have a large yard, and the kids play out every chance they can.   My yard requires quite a bit of coverage so, when we can, we take the organic route to solve problems at each opportunity.

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.

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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.


PVC cutter;
Channel lock pliers
Measuring tape
PVC cement

Step 2: Assembly

I replaced the original 1" elbow (90) that turned downward to my ground-line (to feed the zones) and put a T-fitting on there.

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:

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.

Good luck.

Step 4: Updated: 6/28/13

I have since updated the design to handle pressures issues that arose as well as a way to purge the chamber to add more of your desired solution as back pressures in the line with render the reservoir quite full.

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.

Step 5:

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    16 Discussions

    Joe Bailey

    2 years ago

    Our big problem is not flying bugs but Chinch" bugs that eat the grass and roaches that eat decaying mulch, leaves etc...we can't put anything on the lawns that kills; we just chase them away to the neighbors and hope they die running back and forth...LOL

    Joe Bailey

    2 years ago

    I live in FL and I have a "fertigator" system installed in the sprinkler system now...They have gotten too big and can't address the needs of each individual...So, already having the necessary parts in place: my question is, where can I buy liquefied garlic and fertilizer???

    Stephen Inoue

    3 years ago

    Brilliant idea! You should design and patent an easy inline adapter that lets people fertilize their lawn (as well as your Mosquito solution).


    3 years ago

    Great idea. Can you tell me how you meter the solution into the flow stream with your new setup. With the original you used an Ortho or similar that has an adjustable metering valve. How do you do it with your new design and is it adjustable?


    Reply 4 years ago on Introduction

    It worked well.

    I used a garlic and mint mix from a non-toxic provider we found. A local store.

    A tree cutter dropped a section of fence on it and destroyed it. But, when it worked it worked well.

    I added a check valve to keep things from traveling back.


    Reply 3 years ago

    I keep finding myself looking at this page every mosquito season. I dont quite understand the design after the updates. Did it not work well before the update? Thats how I would prefer to build it


    5 years ago on Introduction

    Can you give a little more detail about how your venturi is setup and if there is a way to limit/ration the amount of mosquito spray? I see what looks you might have fiberglass and glue in the bottom of your spray canister. Is that the case and then you just drilled a small hole at an angle to get the venturi affect?
    I love your idea and plan on incorporating it with the sprinkler system that i plan to install in the spring. I was also thinking that I might be able to replace the manual ball valves with an valve with a solenoid (maybe one from a sprinkler manifold like this:
    As i said, I don't have a sprinkler system yet but my hope would be to hook everything up to a timer so that when my first zone turns on, the valve for the bug juice also opens and then closes after a few minutes (timing is tbd). Then repeat this when the next zone comes on.


    6 years ago on Introduction

    As a Licensed Irrigator i MUST comment on the fact that you have a Pressure Vacuum Breaker on what is in escent a Fertigation system; which, isn't rated for back pressure only back siphonage. Texas State Code dictates that any system that introduces chemicals into an irrigation system must be equipped against both requiring a reduced pressure zone assembly.

    2 replies

    Reply 6 years ago on Introduction

    I appreciate your comments. Could you clarify the concern? Pressure? Or contents?

    I wasn't concerned about code as a) it's not for sale, b) it's removable, and c) garlic and peppermint aren't a chemical--except to say garlic and peppermint have a "chemical makeup". I run organic house and we don't use pesticides.

    Please, comment.


    Reply 6 years ago on Introduction

    I was Just inputting that if is connected to municipal water supply it needs to protect against back pressure; which, a Pressure Vacuum Breaker(PVB) isn't. The backflow pictured is a PVB and are only rated for fertigation if there is no risk of Backpressure, ie a broken city main. Yes, a PVB has a popet valve but this valve doesn't create an air gap around the seal. And while i don't have a particular opinion on the contents, it is still a contaminant to the public water supply. If you do install a Reduced Pressure Zone Assembly(RP), you may need to check on the state of the pressure at the heads because RP's do create a higher pressure drop on backflow TCEQ License # LI0020599


    6 years ago on Introduction

    This is great. I am planning a a full outdoor cabinet with several feeders for insecticide, and different fertilizers. (I live in vegas where keeping a lawn alive is an all out war during the summer).

    I think its very important to point out, as you did, that this rig goes AFTER your backflow preventer. If someone were to install this before the backflow preventer and use more toxic chemicals than you it could cause a lot of harm to people in the house or contaminate other people's water. My home's sprinkler system does not have its own backflow preventer, there is just one for the whole home system to protect the city water, so I will have to install one for the sprinkler system.

    1 reply

    Reply 6 years ago on Introduction

    I put an update out for the sprayer. Combats pressure issues and better re-filling. I hope to tear down and re-submit the whole thing in a more presentable way, but for now I can say it's leak-proof and does the job quite well. Thank you much for the comments too.


    6 years ago on Step 3

    Very well done instructable. Awesome job dude.


    6 years ago on Introduction

    Great work. I've had this idea since purchasing my first house but I've never attempted to do it. Plumbing and I have a long sorted past. Its awesome to see somebody actually put this in place. Hope to see any upgrades or recommendations in the future. I have no idea what a venturi is but I'm going to be googling the heck out of that next. When I was a kid my parents use to buy lawn fertilizer in 10 gallon containers that has what I suspect a venturi is on it that you hooked up before your hose then basically the whole hose would distribute the "product"..... ok now you got my brain really turning. Thanks! This is an awesome post.


    6 years ago on Introduction

    This is such a great solution, it falls into the category of "I can't beleive nobody has done this before"

    great work