I used it regularly when I was at work, Mind you we would be measuring perhaps 2 foot of it in the bottom of a storage tank. we used a steel measuring tape with the cream on the last 4 or 5 feet. a weight on the end all fed through a small hole it the roof of the tank. Periodically we would drain the water off. This was from un processed hydrocarbon known as Condensate that fell out of the natural gas. This was done both offshore and at the gas terminal. On shore in was in Bonded tanks inspected by HMRC so you didn't want them taxing water.