I think there are several conversations about this. I think it depends on your lines. The softer, thicker lines will absorb more than the Bevflex stuff that is thinner and harder. I also don’t think that there is one correct answer except “as often as is necessary”. But one thing I do know is that funk can be in your beer lines and make you think that your beer is contaminated or just generally wrong. Then you may clean your lines and realize the beer is just fine. I went for maybe six months without issue and then cleaned them twice within a month. I have four lines running at all times and my taps are in the bar and the draft fridges are on the other side of the wall so cleaning the lines is a bit of effort. I have an empty keg right now so this weekend sounds like a good time for it.
I thought my beer had developed on “off” flavor, but after cleaning the lines it was fine.
BLC is what I use. Probably should clean more often, as it is suggested to clean at least every two weeks.
Flavor impact depends on a lot of factors including what is growing in the line. I have had beers from horribly infected lines with lots of DMS in bars and even taprooms. At home, the infections have been subtle, just a feeling that the beer now is not as good as it was 2 weeks ago. I usually clean lines when the keg kicks.
In bars, I always ask if the beer I order is the first pull of the day. The bartender is advised that I would like the second pint out of the tap, not the first one. The beer that sits in the lines is not as good, for some reason.
That’s why all the bartenders in Europe allow the beer to run free for a few seconds before placing the glass under the tap.
BTW…I was the winner of the Bartender Beer Pouring contest at the Heineken Brewery in Amsterdam.
I clean my lines once a month whether they need it or not (ha ha!) and I totally agree that the best advice is “when they need it”. Don’t forget to periodically disassemble and thoroughly clean your taps. I gave the lines a good 15 minutes of recirculating line cleaner only to discover an extraordinary amount of black gunk in the taps which the cleaner missed even though I occasionally worked the taps on and off while the cleaner flowed.
If I have to clean the keg that I’m replacing, I might as well clean the lines too. I typically fill my keg with hot PBW, run about a quart through the line, let them both sit for an hour, then flush again. Then water, then Star San. Every 2nd or 3rd time I change a keg I will use BLC instead of PBW. This works for me because I don’t typically have “extra” kegs that are full and waiting for a spot in my kegerator. When a new beer is ready to keg, I usually take the keg that’s closest to empty in my kegerator and empty/clean/purge it right when I keg my new batch. I guess I need to drink more
I only spent $25 between a cheap submersible pump and a ball lock barb adapter. I end up using about 1-1.5 qts to clean my kegs. I think the hand pumps people grab from the hardware store is usually about $10. A bit more expensive than using CO2 to clean from a keg, but I think it’s cheaper in the long run. I clean between every keg, usually until I remember I’m cleaning the lines.