I am going to show you how to make a pressurized spray bottle from an old 2-liter pop bottle. I had a store bought sprayer but it required that I actually pump. Since I am very lazy I made this so my air compressor could do all the work.

Step 1: Materials

I made this out of some leftover plumbing odds and ends I had. This is my first instructable so feel free the let me know where I can improve.

Materials :

PVC
1 1/2" Tee
1 1" adapter
1 1" x 1/2" Bushing
2 1/2" plugs
1 piece of 1/2" pvc pipe about 1" long

Brass
1 1/4" hex nipple
1 1/4" x 2" nipple
3 1/4" x 1/4" barbs
1 1/4" valve stem

Other
1 rubber tip blowgun
1 1/4" quick connect stud
purple primer
pvc cement
teflon tape
5' of Polyethylene Tubing 3/8" o.d. x 1/4" i.d. 165 psi

Tools
1/2" drill bit
Drill
ajustable wrench

Step 2: Pressure Test Adapter

First off I am going to modify the lid so that I can do a pressure check on the 2 liter that I am going to use.

drill a 1/2" hole in the bottle lid
Wrap teflon tape around the threads of the quick connect stud
Thread stud into the lid

Pressurize to about 100 psi. If it explodes entertainingly use a different bottle.

Step 3: Assembling the PVC Fittings

Now we are going to put together most of the pvc pieces. I widened the hole in the lid just to give myself a little more room to work but it is not nessesary. Remember to use purple primer and PVC cement on every step.

glue the lid inside the adapter
glue the bushing to the adapter
glue the piece of PVC pipe into the bushing
glue the tee fitting verticaly onto the pipe

Step 4: Brass Fittings

Now we are going to assemble the brass fittings. When you are drilling the hole in the plugs you will probably have to work your way up to the 1/2 inch bit to keep it from getting bound up. Use teflon tape on all brass fittings.

Drill a 1/2" hole in both the PVC plugs
Thread the strater valve into one of the plugs
Attach barb to 2" nipple
Thead 2" nipple/barb into the remaining PVC plug
Attach barb to the other end of the 2" nipple
Attach the hex nipple to the blow gun
Attach the last barb to the hex nipple

Step 5: Finish the Sprayer

Now we can put everything together. Use purple primer and PVC cement on both of the plugs.

Glue the valve stem/plug onto the tee fitting at the horizontal branch
Cut a piece of tubing approximately 13" long and attach it to the barb on the inside of the plug
glue the barb/plug to the top of the tee fitting with the tube going inside the tee
Attach the remaining tubing to the last two barbs to connect the bottle to the blow gun

Now just fill the bottle half way with water, pesticide, herbicide, or whatever you want to spray. Screw on the sprayer assembly, pressurize, and spray.

I keep the pressure on mine at around 60 psi. I tried going up to 80 but the bottle lid came free of the adapter so I had to turn it down a bit.