there are actually three types of valves at lowes. you have the ball valve alone. then you have the single
union ball valve, not a big fan of these. then there is the true union, the ball valve captured by unions on each end. i tend to buy true unions when i need a ball valve somewhere. i have found that if i needed to control the flow of something than there is a good chance that i may need to remove it at some point. i think the cost difference between getting a true union and just a ball valve is not enough to care. so i just get the unions. this of course only works for pipeing less than 1". once it gets above 1" it gets really expensive to get the true unions.
G~
