Fowl smell in bathroom
Fowl smells related to plumbing can have several causes. Here's a few potential issues that you can check. If none of them solve the problem you may need to call a plumber.
1) Look at your pedestal sink drain connection. Is there an an elbow connecting to your drain or a P Trap? A p trap is a pipe shaped like the letter "p" (hence the name) and it prevents sewer gas from rising into the bathroom. **sometimes an apprentice plumber puts in a pedestal without a p trap because they are fairly difficult to install, and ALL fixtures need P traps. If there is no P trap, then you need to put one in. It will be a tight space, but you may be able to do it yourself.
2) Do you have a floor drain? If so, your sink will need a trap primer at the drain. Or you can pour water into the drain from time to time before it evaporates from the trap
3) If the smell is more of a sulfur type smell and it appears from running water in other places in the house, then it could also be due the type of tank you have if you are on well water
My offhand guess is that number 1 is your issue.
Without further info, those are some of my best solutions so far, but if none of these are potential solutions, then make the following tests
1) close the door to the bathroom and leave it for an hour or two. Return to the room. Do you smell sewer smell? Is it in the entire room or more concentrated in a certain area? If you don't have a floor drain and its everywhere, there could be a missing P trap from a fixture, a lose toilet flange, a cracked drain pipe
2) without running water, smell your drain. Does it have a sewer smell? Then the P trap either is not present or you need to clean the drain with a drain cleaner due to a list of reasons
3) run water. does the sewer smell increase or does one suddenly appear. Is the smell more a different odor than sewer. See if it is the water itself. If so, check other places. If they do not have the smell then you may have recently installed your sink and there is some smell related to the new valve. Then you would need to use it some more until it disappears.
Check the top list, though because I really think you're just missing a P trap
Sewer breaks below the slab, an open pipe somewhere, some issue with the water supply, are among some other issues but that depends on the test