Eijiro (embedded in a long sentence.)

WWW images certainly confirm the meaning. 76k hits - it's amazing it's not in a dictionary.

Found this expression today on an explanation sheet related to the operation of a 
hotel or guest house (minshuku) and noticed it was not in the database. Weblio 
mentions it only as "storage tank", and the other dictionaries i have access to 
don't have it. What is meant here is specifically the kind of tank in a building from 
which people draw hot water for their bath, shower, etc.

At the moment the database returns this:
貯 【おさむ】 Osamu (u) NA
湯槽 湯船; 湯舟; 湯槽; 湯ぶね 【ゆぶね】 (n) (1) bathtub; (2) boat with a bathtub 
rented to customers (Edo period); ED
This does not help any user who doesn't already know the expressions 貯槽 or 
貯水槽... and anybody who does know those expressions understands the 
meaning of 貯湯槽 without a dictionary... :-)