I have an inline tube with an 18mm joint on it. What is the best way for me to plug it up so I can fill it with simple green and let it soak overnight? I've tried the paper towel route, but it eventually gets so saturated that it seeps through the paper towel. Is my only alternative getting rubber stoppers or corks? If so where can I get my hands on some without having to order them online. Oh and what size stopper would I need to purchase. Thanks in advance.
I carved one myself out of an eraser. Or buy a mr waters rubber stopper thingy. Oh there are also GonG plugs that stay secured by a small keckclip. You might be able to find one in stores but are also available online.
The best thing I've found for 18mm joints is wine accessories, the stoppers designed to save a bottle of wine overnight are around a buck each and work perfectly. They look like this, I got mine from amazon because I was ordering a few other things, but you could probably find one pretty easily.