I find that my go to online stores, Great Fermentations and More Beer, have both stopped carrying the homebrewer sized (maybe quart) Five Star Liquid Line Cleaner (often just called LLC).
Can anyone say why, and more importantly, how are homebrewers cleaning and sanitizing their tap lines these days if they can’t get LLC?
Thanks and Cheers! 
I use sodium hydroxide for cleaning my beer lines, but that is a very hazardous endeavor for anyone to employ. Gloves and eye protection are mandatory and avoiding any splashing or spilling is a requirement.
I only use cobra taps on my kegs, so there isn’t much to clean and I am able to pull the entire line out and hang it up for flushing and draining. For a caustic treatment, I fill the line fairly full with RO water and then add a small amount of the sodium hydroxide crystals into the line and then hang that line up with its ends up. I use a large spring clamp to hold the line ends securely and allow me to hang the whole assembly over my brewery sink. After a few hours and a gentle manipulation of the hose ends to bring the solution into contact with all extents of the line, I drain the solution into the sink and flush with water. If the line isn’t clear after that treatment, I do it again.
The line is then ready to sanitize, reassemble, and use.
Look for a different brand. I find line cleaners at both places you mentioned. I’ve used the BLC from MoreBeer but not the brand I found at Great Fermentations (it probably is still a good product, based on the merchant selling it).
I typically remove the faucets, rinse my lines with water, then run half the line cleaner through, let it sit for at least ten minutes, and run the other half through.
While I’m letting the line cleaner sit in the lines, I disassemble and clean the faucets in the sink using a “test tube brush" kinda thing. Then apply some keg tube to the gaskets and reassemble.
After running the rest of the line cleaner out, I reattach the faucets and then rinse the lines and faucets with StarSan.
I use BLC
Since I have beer engines and I can’t use a caustic, I use PBW. I clean my lines, engine and keg simultaneously (I thoroughly clean my keg with hot soapy water first) after finishing a keg. I simply pull the PBW solution through the system for about 20 min. The first few pulls I dump as it contains most of the “gunk” that has collected through the lines. Then I recirculate the mixture.
I would imagine you could do the same thing and recirculate PBW through your system by draining into a second keg then and repeating the process.
You cannot beat sodium hydroxide (aka lye, caustic soda) for line cleaning. It’s sold in solid form as drain cleaner. It dissolves organic substances quickly. As Martin indicated, it’s very (very!) dangerous stuff. Don’t let those organic substances be part of your body.
BLC works alright. Give it a long contact time. BLC is a weak solution of potassium hydroxide, which is a close equivalent to sodium hydroxide. Brewmeister alkaline wash is far gentler and works pretty well.
I don’t want to mess with caustic so I run PBW or Alkaline Wash through and, after letting it sit for a while, flush it out with Star San. Can’t say I’ve ever had something come out tasting bad, unlike many bars that supposedly clean their lines.
And…don’t overlook merely replacing lines periodically. When they came out with the anti-microbial lined tubing, I went whole hog and replace all of my lines every couple years. I also went back to Cobra taps (stainless for most) for keezer dispensing. I have one refrigerator with 4 taps on it, but rarely use them unless a big party or similar event justifies their use.
Looks like More Beer still has BLC
I got an adapter kit for the pump that came with my keg washer, so I’ll recirculate the following:
Hot water
Acid solution - got a bottle from our club’s host brewery to try out
PBW in hot water
Pull the faucets and clean with PBW and pipe cleaner as necessary
Hot water rinse
BLC in cold water
Cold water rinse
Star San in cold water
Quick cold water rinse before putting beer back on
I just use PBW… dissolve it in hot water and circulate… That way I have one thing for cleaning everything… You use StarSan to wash the away the PBW (sodium percarbonate) and sanitize at the same time… 2 steps.. done.
Like Martin, I too use caustic (sodium hydroxide) to clean my beer lines. BLC is also sodium hydroxide. I mix 2 ounces of caustic in a gallon of hot water in garden pump sprayer and hook it to my beer lines. A word of warning when using sodium hydroxide. be careful w not the other way around. When mixing it, always add the caustic to the hot water. This will keep the possibility of getting burns from potential splattering from the heat generated when adding a strong base to water (the same goes when adding a strong acid to water, always add alphabetically). Gloves and eye protection are mandatory, as Martin mentioned.