Tanks

It is cold, it is hot. it is colder than hot, now it is hotter than hot then it goes cold again. It seems like the water heater in older buildings such as my sisters new apartment is loco, one minute it is happy the next it is going crazy and becomes very very hot. I wonder why, i'm thinking that they should just install one of those tankless water heater thingys so that it won't be an issue but then again what do i know