Beer and gumboots

Installing a new beer system many years ago with our mechanical engineer was an experience we will not forget in a hurry; we won the contract to supply new bright beer tanks and upgrade with new service lines and beer dispenser system for the bars, the pub in a rural area in Taranaki NZ , was mainly supported by farmers and travelers ,after several days of work we completed the project and enjoyed beer with the locals ,the beer tasted terrible not that anyone complained as the pub was getting busy we asked others what they thought but no one complained, after sampling more beer and extensively checking the beer system we called the brewery and was advised to empty the tank ? what 20,000 L of beer down the drain ??We did so to find the cleaner had left his mop and gumboots inside the 20,000 L SS Bright beer tank bugger no wonder beer was not tasting to good, we changed to another vessel and shouted the bar free beer the cleaner got heaps by the locals for leaving his mop and gumboots in the beer tank.