The boiler is not working.
cal-DA-ia — three syllables, stress on the second.
Report this immediately — a broken boiler means no hot water and no heating. Italian hosts are responsible for maintenance.
'Caldaia' = boiler (the central heating and hot water unit). 'Non funziona' = does not work. In Italian apartments, the 'caldaia' is the central unit that provides both heating and hot water. If it breaks, both systems fail simultaneously.
Non c'è acqua calda.
There is no hot water.
Report the consequence of the boiler failure
La caldaia fa un rumore strano.
The boiler is making a strange noise.
Report unusual sounds before a full breakdown occurs
Il pilota della caldaia si è spento.
The boiler pilot light has gone out.
Some older boilers have pilot lights that need relighting
Italian Airbnb hosts are legally required to maintain appliances in working order. A broken boiler qualifies as a significant service failure. If the host cannot arrange a repair within a reasonable time, you are entitled to request a partial refund through Airbnb's resolution centre.