What do we use for plumbing?
Water systems in ancient times used gravity to move water. They used pipes or channels usually made of clay, lead, bamboo or stone. Today, water-supply systems use a network of high-pressure pumps, and pipes are now made of copper, brass, plastic, or other nontoxic material. Drain and vent lines are made of plastic, steel, cast-iron, and lead. Lead is not used in pipes today because it can be poisonous.
The 'straight' sections of plumbing systems are of pipe or tube. A pipe is usually made by casting or welding, where a tube is made through extrusion. Pipe usually has thicker walls and may be threaded or welded, where tubes have thinner walls, and needs special joining techniques such as 'brazing', 'compression fitting', 'crimping', or for plastics, 'solvent welding'.
As well as the straight pipe or tubing, many fittings are required in plumbing systems, such as valves, elbows, tees, and unions.
Plumbing fixtures are designed for the people who use the water. Some examples of fixtures include water closets (also known as toilets), urinals, bidets, showers, bathtubs, utility and kitchen sinks, drinking fountains, ice makers, humidifiers, air washers, fountains, and eye wash stations.
Broken boiler vs. plumber
There are repair jobs, that almost anyone can do themself, but broken boiler isn't one of them. Boiling hot water and immense pressure - those are the things that define boiler, and also the things you should be wary of.
Calling in professional plumber isn't any shame in this case, it is necessesity. It is different from a ticking bomb, but close enough, especially if the safety valves are at fault. All in all, you need expert on this - let him do his job, and relax. He is aware of the risks involved and already knows how to avoid any mistakes. All you need to do is coffee and maybe some snacks, while he do his job.
If you are not convinced by this, and ready to repair you boiler alone, all i have to add is this: search the internet for movies of exploding boilers, I dare you.
About history of plumbing
Plumbing originated during ancient civilizations such as the Greek, Roman, Persian, Indian, and Chinese cities as they developed public baths and needed to provide potable water and wastewater removal, for larger numbers of people.6 Standardized earthen plumbing pipes with broad flanges making use of asphalt for preventing leakages appeared in the urban settlements of the Indus Valley Civilization by 2700 B.C.7 The Romans used lead pipe inscriptions to prevent water theft.
Plumbing reached its early apex in ancient Rome, which saw the introduction of expansive systems of aqueducts, tile wastewater removal, and widespread use of lead pipes. With the Fall of Rome both water supply and sanitation stagnated?or regressed?for well over 1,000 years. Improvement was very slow, with little effective progress made until the growth of modern densely populated cities in the 1800s. During this period, public health authorities began pressing for better waste disposal systems to be installed, to prevent or control epidemics of disease. Earlier, the waste disposal system had merely consisted of collecting waste and dumping it on the ground or into a river. Eventually the development of separate, underground water and sewage systems eliminated open sewage ditches and cesspools.