I'm posting this as a question/discussion rather than to the synonyms thread, as I'm not entirely sure on the exact American spelling. Perhaps a hyphen would also be better (ie. "gray water") rather than one combined word.
It should be a combined word, not hyphenated or with spaces.
greywater used in many American contexts. (Not sure if it is used more often than
There's no real consistency -- it's spelled both ways on EPA's site, for example. (They also spell it with spaces sometimes.)
Bottom line: it's a gray area, I don't think it matters much...
(Sorry, couldn't resist.)