Inland Waterways Diesel & Pumpout Price Survey
This is an interesting listing, that could go out of date quickly, but at the moment seems to be updated (last update 17th Oct 2021) each of the entries also has the date of the last update, so if you find different information please send it in an email to the site owner (details on the page)
We have added it to our list of Useful links and web pages page