[luther1]

Wouldn't use filtered water to clean cars.
It will remove any protective wax and might damage some of
the water based paint that's now used on new cars and vans.

You couldn't be more wrong. Base coat is water based,lacquer isn't. Nearly all cars are lacquered and even if they weren't they have been oven baked so wfp would be no different to rain.

[oldman]

I was advised by a supplier of water purification equipment that it was OK to use pure water as a final rinse process but not to use it to actually wash the car as it does tend to strip the wax.

After you have washed car with solution that normally leaves behind some sort of protective barrier then rinsing of the suds is OK.

Your supplier is is talking nonsense.

[HampshireWindowCleaning]

There seems to be quite a split in opinion as to wether it's safe to clean cars with wfp's and pure water, not really what I was hoping for as i'm none the wiser

[home6442]

I was asked to clean a few touring caravans and because I own one myself
know that the paint can be easily damaged.
So decided to do a bit of online research and from what I read decided it wasn't worth the risk.
If filtered water can damage certain metals and some plastics then what chance would car paint
have.
Like all the guys who posted here I am no expert on filtered water or car paints.
Your best option is to check it out for yourself elsewhere and then decide.
Plenty of info out there.

[luther1]

I worked as a paint sprayer for ten years before becoming a window cleaner and its a fact that if you use the correct brush pirified water will not damage the paint or plastic. There are even car washes now that use pure water now with a superb ro setup.