re: Learn me on tankless water heaters

as others said they have to be flushed and cleaned every year. my dad has been in the plumbing business for 25 years and I just built a house with 2 standard 50 gallon gas water heaters instead of an instant. He sells more of the regular gas ones then the instant. my input but they seem to work well but they do have maintenance that I'm sure no one tells the owners about.