Haven't tried oregonpapa's adjustment, but I have a VPI 16.5 and was surprised when I cracked one tube the second month I was using the machine. I always remove the tube before closing the lid, so it wasn't that, it just cracked in normal use, and suddenly I wasn't getting proper vacuum. I have another tube I use, but I taped the broken one up and am still using it occasionally to clean moldy records, just need to replace the tape every so often as it comes unstuck with the moisture. Looking at the way the tube is made it seems like it's a weak point in the design. Conspiracy theories aside, I'm sure VPI is quite happy selling $30 replacements, or you can spend $70 and buy their stronger Delrin tube..