The house we Just moved into at the 1st of the year was just recently re-piped (with copper of course). Since the first day and up until now 3-1/2 months later, we can still smell a very pronounced "Oil" smell in the tub/shower upstairs(hot water only). The 1/2 bath downstairs with a sink and toilet(15-20 feet away from water heater =/- 10 yrs old), have no odor at all. The kitchen sink or dishwasher(50-60 ft away from water heater) have no odor either. The stall shower, toilet or sink upstairs(furthest from water heater) has no odor. Only the tub/shower(closest to heater, probably because it is almost right above the water heater located in the garage) has a very pronounced smell of oil. Each and every time you run the water it's there. The water appears as clear as the rest of the locations. The water in the toilet and sink, however, have no smell at all. The oil smell, does not smell like "flux", it smells more like the oil used when threading galv. pipe. there is no sign of anything wrong with water heater or the pipes, etc. around the area where it is located and no oil smell is present their either. Just in the tub/shower upstairs bathroom. Either we get used to it while showering, or it gradually goes away while showering. Our four boys all shower/bathe in that bathroom. Can it be harmful to them? I would appreciate any reply. Thank you in advance and enjoy your days! :)

So you are saying the tub in that one bathroom but not the sink in the same room has the smell, right. Well that narrows it down, it must be something in the hot supply pipe to the sower mixing valve. Harmful, we'll have to see but tell the boys to shower esleswhere until this is solved. Do you know how to open up the guts of the shower mixing valve?