I use vinegar quiet often and have never had a problem with elastic or PUL breaking down.
eta: it does work well as a fabric softener too... we have really hard water here.
__________________
Lis + Caitlyn 4 + Lachie 21m
co-sleepers, extended breastfeeders, babywearers
and long time MCN'ers!
BLOG- updated 1st November - Pixie Hat