Vinegar should be #1 against hard water.
You can try a razor blade too. Like taking off an old sticker. Be super careful not to catch an edge, it will cut into the glass if you do it right. I will leave scrape marks if your not careful. Like anything, make a test spot somewhere you won't be looking at it every time you drive your car.
You can look into CLR too. I wouldn't risk it on a car but it works great in bathrooms.

Update
 

Yes, I've thought about this too. It's just not normal to have this much of a problem after only one wash.

I'm going to find someone to do a test and see what's going on with my water.

I've been wanting to try CLR but haven't been able to get any yet :(


---------------- UPDATE ----------------------

So like I said, I got some 3M rubbing compound, masked off all the edges, and with my orbital polisher and a lot of elbow grease I was able to achieve pretty good results after a couple of hours.

http://www.the370z.com/members/quarr...fore-after.jpg

I applied some rainX to see if that helps with the beeding and we'll see what happens next time I wash the car...

Can you get enough DI or distilled water to do a final rinse? Both are rather expensive when bought by the gallon but may be cheaper than having to polish your glass.

Edit: FWIW, CLR is lactic acid. Approximately 10x more "acidy" than acetic acid (vinegar), so be VERY careful if you use it on a car.

Thanks for the tip. And yes, like Maddog originally suggested I'm looking into getting a DI filter to do the final rinse.

Just so I know... How do you use the vinegar? Do you just wipe with it? or let it sit for a while?

I just dampen a cloth enough that it doesn't drip, wipe the glass (being careful not to get the vinegar on anything else) a few times, and rinse with plenty of water. Make sure to rinse any places that water might collect extra well. May have to repeat a few times for heavy deposits. Pretty much the same procedure that many use with glass cleaner - just a more thorough rinse.

vinegar needs to sit a good 5-10min inorder for all the calcium to break down. so i usually place a towel over the area i want to apply (place something heavy on it so it doesnt get blown away if outdoors) and pour the vinegar on the towel. keep applying more vinegar if it starts to dry.

Hey all. What about that CLR cleaner? I remember I had to use that stuff to clean my shower and glass while living in the desert.


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no idea. i will warn not to use harsh chemicals as it can damage the seals. it aint like ur car is a toilet/bath tub