plumbing brings water into your house and waste water back out to be treated . there are water pipes made of copper , galvanized steel plastic and sometimes even lead or wood the water comes into the house and quickly has a shutoff valve , there may also be a ground wire clamped here as close to where the pipe leaves the house as posible The water then heads to the water heater where it may tee in to two pipes , one hot and one cold. The hot and cold water is piped to the sinks and such then is let down the drain pulling air down from the vents behind it .