Adrianmsmith don’t use that thread locker, it’s permanent and if it’s for the nut at the back, it will leak again within a few years if you regularly use the steam. This is because it sets hard, the constant expansion and contraction as the fitting heats and cools eventually breaks the seal.
I stopped ACS from using this product some years ago (probably 3+), and they now use Loxeal 18-10, which is easy to undo as it’s not permanent, has PTFE, is WRAS approved and sets remaining slightly flexible.
https://tinyurl.com/2cjnyrmv
P.S. Unfortunately too many espresso machine manufacturers use Loctite 272 and similar permanent thread lockers, because it’s cheap, sets quick and is easy….hence fittings often leak and get damaged when people try and remove them
