Use of DI water in washer system

[NINJA59]

I had a dabble in the manual today and saw an interesting note from BMW to not use "pure water" in the washer system.

Can anyone provide me a reason as to exactly why?

Problem being, like many of the UK Kent guys will know, the water parts per million (ppm) count is around 240-250 measured from the tap. Which means leaving any water on the surface of the car in any mild warm weather will leave water spots within about 30 minutes (it is among a number of reasons I have access to filtered water for all final rinse applications during washing on an average day (or like on Friday's wash in mildly direct sunlight the full process with no water spotting ).

I do have access to mildly filtered (Brita), but that is a pain when I have a ready made 0ppm source for bottle mixing when detailing.

[BMWrules7]

Originally Posted by NINJA59

I had a dabble in the manual today and saw an interesting note from BMW to not use "pure water" in the washer system.

Can anyone provide me a reason as to exactly why?

Problem being, like many of the UK Kent guys will know, the water parts per million (ppm) count is around 240-250 measured from the tap. Which means leaving any water on the surface of the car in any mild warm weather will leave water spots within about 30 minutes (it is among a number of reasons I have access to filtered water for all final rinse applications during washing on an average day (or like on Friday's wash in mildly direct sunlight the full process with no water spotting ).

I do have access to mildly filtered (Brita), but that is a pain when I have a ready made 0ppm source for bottle mixing when detailing.

Most likely, the risk of freezing. This could damage components.

[lemetier]

Originally Posted by NINJA59

I had a dabble in the manual today and saw an interesting note from BMW to not use "pure water" in the washer system.

Can anyone provide me a reason as to exactly why?

Problem being, like many of the UK Kent guys will know, the water parts per million (ppm) count is around 240-250 measured from the tap. Which means leaving any water on the surface of the car in any mild warm weather will leave water spots within about 30 minutes (it is among a number of reasons I have access to filtered water for all final rinse applications during washing on an average day (or like on Friday's wash in mildly direct sunlight the full process with no water spotting ).

I do have access to mildly filtered (Brita), but that is a pain when I have a ready made 0ppm source for bottle mixing when detailing.

Pure in the context of just water with no additive or dedicated fluid. It's to keep the lines from both freezing when cold and steam from absorbed heat in the places it passes really hot bits.

[j_d_valle]

If any part of the washer trayectory is metal it will corrode if its just pure water with the engine heat cycle. Thats all the i can make of it.