Let's start with 42-72. Landlord to provide fit premises.
(a) The landlord shall:
(1) Comply with the current applicable building and housing codes,
My note: Lack of hot water may be a code issue. Call the city code enforcement department.
(2) Make all repairs and do whatever is necessary to put and keep the premises in a fit and habitable condition.
(4) Maintain in good and safe working order and
promptly repair all electrical, plumbing, sanitary, heating, ventilating, air conditioning, and other facilities and appliances supplied or required to be supplied by the landlord provided that notification of needed repairs is made to the landlord in writing by the tenant, except in emergency situations.
My note: 18 days obviously not "promptly."
Unfortunately, 42-44. General remedies, penalties, and limitations is not help.
You can read the statutes at:
https://www.ncleg.gov/Laws/GeneralStatuteSections/Chapter42
Is the problem with the WH something you can pay to have fixed and then seek reimbursement from the landlord? You're not allowed to withhold rend without a court order but if it's not an expensive repair it might be cheaper to have it fixed rather than go to court.
Meantime, call the city and see how that goes.