Okay now that I have hot water I've noticed that in one of the bathroom's the hot water coming out of the sink faucet has a faint "oily smell" to it (cold water is fine from all taps), sort of like there's WD-40 or something similar mixed in with the water. The shower in that room doesn't have that smell coming out of that faucet. The kitchen hot water doesn't smell either. In the other bathroom the hot water from the sink maybe has the smell (it's much fainter if it does) and the shower doesn't seem to have it.
There was some remodeling done on the house before I moved it (like the new water heater in my previous post) and in that bathroom they at least put in a new tub/shower but I don't know if any of the plumbing in the walls/floor was actually changed.
Is this smell something to worry about? Will it go away in time if I just continue to use it? Is it actually safe to use that water for like shaving while it still smells?
I hadn't really run much hot water through that faucet until recently so not a lot has run through that hot water pipe yet, I don't think. Given the size of that bathroom and the location of the fixtures and the new window that was installed I would guess that it was once a half-bath without a tub/shower and they added one and redid the plumbing before they sold it and I moved in. So yeah there's probably some new/modified pipes and stuff in the walls.