Quote Originally Posted by pavlo View Post
I would have thought any grade of piping would do, so long as it is rigid. If you produce a perfect vacuum you will have an external pressure on the pipework of 1 bar. This is minimal compared to the internal pressure that most pipes take. Class C pcv pipe will take an internal pressure of 9 bar for example.
The pressure for a vacuum though is in the opposite direction to which the fittings are designed for. Perhaps could make a difference... but I'm only guessing!