I was helping my friend wash his car and I suggested that while spraying down his car, he should squeeze the garden hose trigger as much as he can to get the water stream to have more pressure. My logic was that by doing so, the water pressure would remove the dirt more easily. However, he refused to do this because he believed that spraying down your car with such pressure can damage the paint. Can anyone tell me if spraying down your car with higher pressure will damage your car’s paint job. Keep in mind that I am not using a pressure washer, I am simply squeezing the trigger of a standard garden hose to its maximum to get more pressure. Thanks.
Your friend is so wrong, it isn’t even funny 
Wow. I could see where a pressure washer could hurt the paint. I know someone who just cut themselves with the stream of water while using one. However, you can even dial those down to a safe pressure to wash your car with. The truck driver at work uses one to wash the semi and box truck every time he comes back from a trip. There is NO WAY one of those garden hose sprayers could hurt the paint. What pressure does he think a touchless car wash runs at? I guarantee it’s a lot higher than a water hose. I would think driving down the road in the rain would be worse than a hose sprayer.
I just found an article at ehow.com about car washes:
There are several different types of touchless car washes available. PDQ is one type of a touchless car wash system that offers customers a special “no-scratch Laser wash system” complete with “Laserdri,” its own brand of a drying system. X-Stream uses a premium high pressure pump called a Catpump 3545 which is able to produce water pressure of about 45 gallons per minute at 1000 psi. It also offers Wheel and Rocker Blasters which specifically target your wheels, rims and rockers for an extra clean car.
45 gpm at 1000 psi!
If you still have dirt/dust/grime on your paint, a high pressure water stream is going to grind that stuff into/against your paint job. Will you see the damage you’re doing? Not immediately. Will it do damage over time? Yes.
It’s best to get the car wet, loosen up the dirt/dust/grime with a car wash soap, and rinse away the bad stuff without grinding it into the clearcoat paint.
Well done, Goldwing. You didn’t jump on the “let’s criticize because we’re so experienced” bandwagon that too often characterizes the Cartalk discussions.
I use a gentle water spray when I wash my car, not the highest pressure on my garden hose.
I learned this from a professional car detailer. Does it matter? I don’t know, but I see no reason to use a higher pressure.
I have a pressure washer, but I would not use that on a car. Too easy to push water where it shouldn’t go.
I have seen a pressure washer take clear coat off a car, but nothing you can get from your hose without a pressure washer will damage the paint.
The pressure of a garden hose won’t damage your paint. It’s remotely possible that it will grind leftover dirt against the paint, as Goldwing has mentioned. But realistically, that’s going to be very minor and very rare. You won’t be able to see it with your naked eye unless you wash it once a week for 10-15 years. The best thing you can do is to wash it very well, and then give it a coat (or two, preferably) of high-quality carnauba paste wax. The wax will help keep dirt loose enough that your initial rinse will take it off, leaving very little actual grit for even the washing stage, much less the rinse.
The DIY car wash sprayers are stronger than a garden hose and I’ve never seen any damage done using them.
Most municipal water systems run around 40-60 PSI on water pressure and I don’t see that as being harmful to the car finish since any abrasive soap is not being sprayed along with the water.
One should not use something with several hundred pounds of pressure and a 1000 PSI? Ouch.
Guess that will take that expensive dealer installed “paint protectant” right off; along with skin.
It won’t hurt the GOOD paint but it definitely will not take any dirt off. It just uses more water. I hate to watch a dirty film on my car.
A garden hose doesn’t have enough pressure to do any harm… or it would be taking your skin off too when you got in front of the stream. It’s unlikely you will even cause harm with a pressure washer unless you blast your car with it at point-blank range. THAT could damage the paint. Most pressure washers also have a gentler setting for washing cars, wood, etc. that won’t damage things.