I live in a condo building, and the sump pump in the basement was running water constantly for several days. When the plumber was contacted, he said to call the Village and have the water tested for flouride to determine if there is a leak in a pipe. When the representatives from the Village came, they said we need a new sump pump. So, the plumber installed a new sump pump, and then, I was told that he poured oil in the sump water, and said that we need to pour oil in the water every six months. A Village representative came after the sump pump was installed, and when he discovered there was oil in the sump water, he was furious, and said that they don't want oil in the pipes. Before we call the plumber to tell him that the Village said not to pour oil in the water, has anyone else heard that this is a recommended practice?
I've heard of using a layer of oil to prevent evaporation or discourage mosquitoes or things like that... but that requires levels be set so the oil stays above the pump inlet at all times, and it assumes that some loss of oil into the exhaust is OK (which is one reason it might need replacing).
If the town said no, I'd say it's a reasonable position for them to take, and the plumber should know the actual rules... so I think it's worth telling him that there was an objection and asking him to explain why he recommended it.