We had a combi okay, hot water whenever you require it, but if somebody turns a tap on when you're in the shower, heavens you know about it! Egg boiler can boil up to eggs at a time full working order small amount of limescale inside but doesn't affect boiling. But when is the right time to replace your boiler, and what should you be looking for in a newer model? No time to network? no problem! these tips are.