For the water filtration we’ve been using Supor PES membrane filters (.1um), supported using a fancy filter holder from Millipore. (both recommended by Laura Sauder from the University of Waterloo). So far this setup has worked pretty well, although obviously a bit slow when there’s a lot of sediment in the water. However, last night the rubber stopper that holds the thing together cracked and got sucked into the vacuum flask. Which is pretty much a one-way trip… It’ll probably stay there forever. So I looked at the Millipore website and they want $100 + shipping for a replacement stopper! It’s a piece of rubber (well silicone actually) with a hole in it. Sheesh.
So after consulting with Russell in our lab, he directed me to Central Services on campus where I bought a rubber stopper for $1.05 and they drilled the hole for free. As a bonus, it actually fits better and is easier to use than the one that costs one hundred times as much from Millipore.
Jonathan Eisen's Lab 
Yeah, you’re a PI… That is a pack of 5 silicone stoppers so they’re really “only” charging you $20 each. Silicone stoppers are expensive no matter the source, solid #8s run about $65/10pack. So buying a molded, one-hole #8 from a notoriously non-inexpensive company like Millipore, well that is what you would expect to pay. You’re not worrying about the chemical grunge in that black rubber stopper screwing up your results so you don’t have to care, others aren’t so lucky. Also if you split that silicone stopper and sucked it into the flask then your vacuum pump is a little too strong for that filter system & you’re setting yourself up for membrane failures.
Yours truly,
A cranky old lab manager
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