Blowing out water lines

I have been motorhoming for 40 years. for 38 of those years I got by with blowing out my lines with only one minor problem that being a cracked waterpump because the water stayed in the pump. Now to the real lesson 2 years ago I bought a newer motorhome with more stuff in it. I blew it our as I have always done and come spring began putting the unit back in service. water poured from places it wasn'lt supposed to. I began replacing what I could but got to an area I couldn't reach. The bottom line it finially cost me just kunder $1000 to fix my leaks. Now I ALWAYS blow out the lines then add tdhe pink stuff to the lines. It's cheap insurance, doesn'lt cost a whole lot and takes no more time really.