I use auto anti-freeze concentrate. Not the 50/50 mix. (why pay for the water and get half the product, right?!?!?)
Never had any problems with the pump seals. I drain and blow out all my lines and supply hoses so they have nothing in them over the winter.
Rod
There's a big difference between drilling out a red tip and using a "shooter" tip. Its like going to a shooting range with a handgun and a rifle to do some long distance target practice. The barrel of the rifle makes a world of difference in target shooting for long distance as does the barrel of a shooter tip.
$30 for a pinpoint accurate shooter tip that give you excellent distance as well is money in the bank every time in the powerwashing business. Its also great for safety reasons because it keeps you off ladders and saves your back because you'll use your extension wand much less often so it's a "win win" in my book!
ACR is a great find for new or old salts in the PW business. We're fortunate to have Tom, Barbara, and crew local to keep us in business. Been dependent on ACR for now 14 yrs. for nearly all of our chemicals, stains, equipment, and repairs.