This appeared in ‘The Confessional’ section of the March 2019 Yachting Monthly:-
Port Vell Tank Blunder

The nautical adventures and misadventures of Hejira, her skipper, and all who sail in her…
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Thanks for the expensive advice. No consolation but even SS tanks would have buckled. It is good to know, though, that the tank failure was due to an external factor and not an inherent failure issue of plastic tanks.