Thanks George for your input.
I like the water comment. Yes water mixes with the brake fluid but doesn't settle to the bottom of the caliper or wheel cylinder.
If the guy wants to test his theory. Get a clean glass jar put new brake fluid in it add some water and mix it up. See if it settles out.
Use Dot4 or the newest stuff Dot 5.1

 

In fact, if you pour an oz of water into a glass of brake fluid the level of fluid in the glass will not rise! Just like alcohol the water combines with the brake fluid (forgot the real word).

 

Don
The word is absorption. Lol.

 

The fluid is also called hygroscopic, meaning it attracts water from its surroundings.

I am not against flushing the system after years of use, but I don't normally do that when I am doing brake pads and or rotors. It's a closed system, and should stay free of moisture if you don't mess with it.

That includes "topping it off" when it's low. It is low in the reservoir because your pads are worn. Once you do compress those calipers, the fluid goes back to the reservoir. If you topped it off, it is now over-filled, and brake fluid comes out of the cap, and it can eat the paint off your booster and other things. Just don't top off. If it is actually low on fluid, you have a leak, and that is serious, but you should see signs at one of the wheels easily.

 

I once was talking to transmission mechanic about my hydraulic clutch, the truck had a separate reservoir. When I told him I suspected my clutch was getting to EOL because the fluid was getting low with no puddles he was absolutely astounded and asked "where is it going?"

DOT 5 is not recommended, unless the car came with it. Not compatible with 3,4 or 5.1. DOT 5 is not the same as DOT 5.1