
NB: "chiotte" is a distinctly vulgar term for a toilet (cf. "shitter"), and shouldn't be used in polite company. "toilette(s)" is just fine if you're asking for the loo generally.
…apparently "toilette" in the singular is Belgium-specific.. According to that article the Belgians reckon that the French use it in the plural because the state of French toilets is such that one must go to several toilets before one finds one clean enough to use.