The word firewaters is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 16
Highest Scoring Words With Friends™ Play In The Letters firewaters
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Seven Letter Word Alert: (41 words)
aeriest, artsier, faeries, fairest, ferrets, ferries, ferrite, fraters, freesia, rafters, rearise, refires, refrets, refries, reswear, retears, retires, retries, rewater, rewires, rewrite, seawife, seriate, serrate, swearer, sweater, swifter, tarries, tearers, tearier, waferer, wafters, waiters, wariest, wartier, waterer, wearers, wearier, wearies, wrester, writers