There is minimal maintenance to keep the water heater running good as new. Here is a quick link to some helpful steps http://www.wikihow.com/Maintain-a-Tankless-Water-Heater
Hello I am Ken From KP Carpentry. Can you tell me more about your built in project? Do you have a design in mind? How big is the area? Can you take a few pictures of where you would like it to go?