Thanks Steve and Craig. You have just resolved the whole “Festo on the suction side” issue for me..

I did a bit of research and discovered that Steve is quite correct. The MAXIMUM vacuum any pump can possibly create is 1 Bar, or one atmosphere. (Stands to reason really as one atmosphere the maximum outside pressure we will ever see, unless we go flying in a pressure chamber.)

If the Festo spec sheet is correct, these fittings will hold any negative pressure that can be applied by any pump. I will continue to use them on the suction side of my fuel system, with the proviso that the correct tube type is used, and it is cut correctly.

Thanks guys.