Hyphens, En Dashes, Em Dashes
Q. Should the word “pre-dewatering” be hyphenated?
A. I reckon hyphenatin’s too good for a word like “pre-dewatering,” though it surely ought to be put out of its misery somehow.
Seriously, we tend to be suspicious of words beginning with “pre-,” which seem to be proliferating lately. What is the difference, after all, between presliced bread and plain sliced bread?
If what you want to say is “before dewatering,” then you can use the word “before.” If you are tempted to say “pre-” because you want to use the phrase to modify another noun (e.g., in the pre-dewatering period), then you can rephrase to avoid the problem (in the period before dewatering).
If you were to write back and tell me that this word is standard parlance in some technical field, it would make me grumpy, but I would tell you that Chicago style is to close up all prefixes unless confusion would result.