kotao

1. cauldron; large pot
   Baka je kuvala pekmez u velikom kotlu. — Grandma cooked jam in a big cauldron.
   Na vašaru se pasulj kuvao u kotlu. — At the fair, the beans were cooked in a cauldron.
2. (in heating) boiler
   Pokvario nam se kotao, pa nemamo grejanje. — Our boiler broke down, so we have no heating.
   Kupili smo novi kotao na pelet. — We bought a new pellet boiler.

A kettle for boiling water is čajnik or kuvalo za vodu, not kotao.