STi Intercooler Waterspray Into 2002 WRX Wagon

I found a great deal on a STi waterspray tank and switch and decided to take it. It came with the reservoir, pump motor, level switch, ~1ft of tubing, and the stock USDM switch. I picked up 20ft of tubing at a hose supply company for $15.
I did a little reading and got the wiring diagrams for the switch and pump, then went about deciding how to wire things up for my install. To compensate for the lack of time delay relay I searched my parts bin and came up with a 555 timer and then hit up Princess Auto for a $5 automotive relay & harness.
I knew that I wouldn't have the IC spray hooked up in the winter and I wanted it installed somewhere "covert" and out of the way as I actually use my trunk... a lot! I came up with the idea of removing the spare tire and putting the tank in that spot- works great after drilling a single hole in the tank mounting bracket and I can use my entire trunk as the cover/floor goes right over top like stock.
Hose and power/ground routing was done along the same routes as the stock rear washer/gas lines & wiring; along the driver side.
Here are pictures of the whole install and a little more info about wiring for anyone out there who may be interested...

Stock WRX intercooler shroud vs. STi with sprayer nozzles- not a huge difference:


Water tank bracket mounted in spare tire well. This is bolted right into the same spot as the stock spare tire hold-down. One hole needs to be drilled in the bracket where the bolt is seen (or where the blue dot is in other pictures):


Showing how the water tank bolts up to the bracket. Two 10mm nuts hold it on. You can just get at them with a wrench while the bracket it bolted down:


The water hose was run along the stock line and I brought it out through this existing bung (drilled holes though the plastic). My vacuum tube for the stock boost gauge also uses this:


The hoses run into the engine bay the same way as the stock wiper hose and wiring harness:


Then it runs along under the various wires, hoses, and what-not to come up in the same spot as the stock wiper hose and connects to the in-line check valve and the tube/splitter combo that runs to the IC sprayer nozzles:


The wiring of the relay to the stock switch and the 555 timer setup. In retrospect I should have used a pot instead of a 10k resistor for the timing as my test 12v source gave 5s but the car power gives 3.5s. With a pot I could have dialed in the spray time exactly. Oh well. Holding down the button sprays as long as you hold it :)


Wiring the switch into the car is pretty straight forward. The basic steps follow for a +12v switched relay that provides ground when "on". If you want detailed wiring instructions leave feedback on this post and I'll put them up.

1. Tap the existing wires for the illumination bulb & wire into the switch.
2. Wire up your relay to be +12v switched on.
3. Run a ground to the IC spray switch.
4. Run the output of the switch to the trigger of your 555 timer circuit (must be ground!)
5. Run power and ground to the 555 timer circuit. Use the same switched power source and ground as the relay and switch.
6. Run the output of the 555 circuit to the +12v switch of the relay.
7. Run the "on" output of the relay (should be ground when "on") to the IC spray pump.
8. Fill the spray tank, turn on the ignition, and spray away!

When winter comes just disconnect the wires @ the tank and tape-off. Cap the water hose and you're done until spring.

Hopefully this will help/encourage others out there to try this. I couldn't find any detailed instructions for this (and none for the 555 stuff) so I thought I'd share it with some pictures to help out. :)

Cheers!