These standpipes are located on Racecourse Rd, Waipukurau and Waverley St, Waipawa.
Taking water from CHBDC supply other than at points authorised by permit is considered to be a breach of the Central Hawke's Bay District Council's Water Supply Bylaw.
Failure to comply with the bylaw is an offence and is liable to a fine of up to $20,000, the council said.
"Fire hydrants are for authorised firefighters, but it is noted that some people are accessing them, illegally to meet their own water needs," according to the post.
"This illegal use can have serious health and safety implications as if damaged; the hydrant may not be available for firefighters.
"It could also lead to chemicals or other contaminants infiltrating into the water system, which can be a potential risk to the health of our community.
Council urged anyone who saw or heard of anyone taking water from a fire hydrant who wasn't a firefighter, to report it on its 24-hour line 06 857 5060.