It depends on the nature of the repair.
Your responsibility (art. 19): routine maintenance work and simple repairs linked to normal use, in particular doors, windows, glazing, locks, electrical fittings, tiling, paintwork, as well as the repair or replacement of taps and sanitary fittings.
The landlord's responsibility (art. 10): he is required to maintain the premises and to carry out all repairs necessary for their preservation. He also warrants defects that you could not have detected on entry (art. 9). A water heater that fails for lack of maintenance the landlord should have provided therefore falls within a defect whose repair is his responsibility.
The procedure to follow:
- Inform the landlord through legal channels (registered letter with acknowledgment of receipt) as soon as possible (art. 18).
- If he does nothing within one month, you can obtain from the court an order setting the amount of the repairs, authorizing you to carry them out, and to deduct their cost from the rent (art. 10).
Never deduct rent on your own initiative: go through the court (art. 10 and art. 21).
This is general legal information, not legal advice. For advice on your specific situation, consult a lawyer admitted to the Bar in Morocco.