grease, light liquid

"Grease trap" is the standard expression used for basins that catch ('lapat') oil, grease, lard etc, separating it from waste water before that goes into the public sewerage system. You can usually find them at restaurants where there's a lot of frying going on. I remember a few years ago the local nursery school was flooded with backed up sewerage because the grease trap was full and clogged up the pipes ... yum.

This is a nice explanation from the Colorado Dept of Public Health: "Grease traps capture the oil and grease from the flow
of wastewater by slowing down the flow of hot
greasy water through the grease trap (actually a tank)
and allowing it to cool. As it cools, the grease and oil
separate out of the water and float to the top of the
trap. The cooler water continues to flow down the
drain pipe to the sewer while baffles prevent the accumulated
grease and oil from flowing out of the
grease trap." See http://www.cdphe.state.co.us/HM/grease.pdf ... no pictures of Olivia or John there, though, I guess they don't have much of a sense of humour.

BTW, I don't think oil trap is bad but if you google for it you'll find lots of references to petroleum oil.

see the ref. links

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Note added at 17 hrs (2007-11-02 08:52:14 GMT)
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here is the link including document - EU Regulation, check the point 5.07

http://eur-lex.europa.eu/Notice.do?mode=dbl&lang=sk&lng1=sk,...