Not every mobile home has on-board plumbing systems. However, those that do operate in a very similar manner to bathrooms in regular, non-mobile homes. The only difference is that the two key ingredients to having a successful plumbing system--the hot water heater and the septic tank--are attached to the home and travel with the user wherever the vehicle may go.
Hot Water Heater
The hot water heater in a mobile home operates in an almost identical fashion to one you would find in a regular home. A series of pipes, typically made from long lasting PVC, connect the sink, shower (if applicable), and toilet water tank to the water heater. The heater itself is typically found somewhere near the rear of the vehicle. In very large models, it may be tucked away under the floor. These provide the bathroom with running water, both hot and cold. As they are not connected to any outside sewer system, however, they will have to be refilled quite often from a clean water source.
A 30 gallon gas water heater typically runs somewhere in the neighborhood of five hundred dollars.
Water from the sink, shower and toilet of a mobile home will empty out into an attached septic tank just as it would if they were in a regular home. The septic tank is connected to these devices through a series of pipes. The septic tank is found near wherever the hot water heater happens to be.
One important thing to remember is that the septic tank is going to have to be manually emptied. The frequency depends on its size, but you should check it often to be on the safe side. Mobile home parks (also typically referred to as trailer parks) will have specific areas these septic tanks can be emptied. Many camp grounds and other places one might park a mobile home for an extended period of time will also have very specific areas and rules regarding the emptying of a septic tank, so as not to contaminate any clean water source.