Typically when I push the pistons back, I stick the bleeder on and expel the manky old fluid out of the cylinders rather than squirt it back up the line. That way you get a gradual change of the fluid over time with all the muck and used fluid being removed.
The dot-5.0 silicone not being hygroscopic is a problem. You will always get some moisture into the system, and as it is not absorbed, it stays at the bottom, at the wheels. There it boils when the brakes are used, and you get fading brakes; and it causes the pistons to rust from the inside.
Use dot-5.1, which is the best for general use, and mixable with 3 and 4.
http://www.gomog.com/allmorgan/brakefluids.htmlDon't agree. Short of having a leak in the system which would be obvious due to fluid leakage, just how/where is water going to get in? The only way for water to get in is via an ill-fitting reservoir cap. Water vapour will obviously get in through the breather but will not be absorbed by the silicone Dot5 stuff. The problem of brake boil due to water in the system is just what the silicone fluid is designed to eliminate. JMO