Tired of water spots every time you wash your car? There are a number of companies selling spotless car wash systems - CR Spotless, DI Rinse, etc. - but they are quite expensive. Here's how I built a setup myself ...and ended up spending way more money!

The water that flows from your hose naturally contains dissolved minerals such as calcium and magnesium carbonates (it is "hard water"). When the water evaporates it leaves behind these minerals causing spots all over your freshly washed paint. Filter these minerals out before washing and voila - no more spots!

At the heart of any spotless system is a mix of special tiny beads which act as "the filter". When a mineral like calcium carbonate is dissolved it, well, dissolves. Think of it as breaking apart into calcium (positively charged) and bicarbonate (negatively charged) due to the polar nature of the water molecules. Some of our special little beads are very good at attracting negatively charged ions and the others in the mix are very good at attracting positively charged ions. Pass your hose water through a tank with enough of this mixed bed deionizer resin and all of the minerals will stick to the beads, leaving pure H20 for your car.

What's the catch? Well, eventually the resin beads suck up all the impurities they can hold and will need to be replaced. And it is EXPENSIVE. The best deal I could find was just under $200 for a cubic foot. I think that is why I ended up spending more money than if I had just bought a ready-made system. I used a full cubic foot in my design versus the smaller tanks of the popular products on the market. Hopefully mine will last much longer before it is time for a refill?

What You'll Need
An 8"x35" "mineral" tank (commonly used in water softener systems) - $60
A riser tube long enough to reach the bottom of the tank - $20
An in/out distributor head - $25
Adapters to go from the thread type of the head (usually NPT) to garden hose thread (GHT) - $30
A garden hose flow restrictor, 2 gpm (use less water to prolong resin life) - $15
A wall clamp to secure the tank from falling over - $35
Two hoses, one from the spigot to the tank and another from the tank to your car - $50
Hooks/reels to hang the hoses on when not in use - $10
A mineral tank-sized funnel to help you load the beads - $10
1 cubic foot of Virgin Mixed Bed Deionizer Resin (not water softener resin!!) - $200

How to Assemble
1) Stand the tank upright and place the riser tube inside, basket down.
2) Put some tape over the top of the riser tube to keep beads out while filling the tank.
3) Use the funnel to help you fill the tank with the resin beads
4) Remove the tape from the top of the riser tube and then screw down the distributor head (I used teflon tape)
5) Screw in whatever adapters are necessary to go from the thread type of the head to garden hose thread (again I used teflon tape)
6) Put the flow control attachment on your spigot to save water / extend resin life
7) Attach your hoses, the "in" side is for the hose connected to your spigot and the "out" side is for the hose that goes to your car.
8) Use the wall clamp to secure the tank and mount your storage reels/hooks near the tank.

That's it! You can now wash your car spot-free with no need to towel dry!

note: In the picture to the left I am using too large of a tank so I filled the rest up with cheap ping pongs balls. When you shop for tanks you'll notice that many state their capacity, but this is for water softener resin! Water softener systems can be "re-charged" with salt by back-flowing the tank and therefore need extra expansion room. With a spot free car wash setup using mixed bed deionizer resin you want the resin to fill the tank without a lot of empty space. To determine tank capacity use the physical dimensions to calculate volume (pi * radius squared * height), not the manufacturers stated capacity.