Bacteria have been shown to live in "premises plumbing systems". The latter refers to the "pipes and fixtures within a building that transport water to taps after it is delivered by the utility". Community water systems have been known for centuries to spread waterborne diseases like typhoid and cholera, however "opportunistic premises plumbing pathogens" have been recognized only more recently; Legionella pneumophila discovered in 1976, Mycobacterium avium, and Pseudomonas aeruginosa are the most commonly tracked bacteria, which people with depressed immunity can inhale or ingest and may become infected with. These opportunistic pathogens can grow for example in faucets, shower heads, water heaters and along pipe walls. Reasons that favor their growth are "high surface-to-volume ratio, intermittent stagnation, low disinfectant residual, and warming cycles". A high surface-to-volume ratio, i.e. a relatively large surface area allows the bacteria to form a biofilm, which protects them from disinfection.
Most plumbers, pipefitters, and steamfitters learn their trade through a 4- or 5-year apprenticeship. Apprentices typically receive 2,000 hours of paid on-the-job training, as well as some classroom instruction, each year. In the classroom, apprentices learn safety, local plumbing codes and regulations, and blueprint reading. They also study mathematics, applied physics, and chemistry. Apprenticeship programs are offered by unions and businesses. Although most workers enter apprenticeships directly, some start out as helpers. The Home Builders Institute offers a pre-apprenticeship training program in plumbing and other trades.
PVC/CPVC – rigid plastic pipes similar to PVC drain pipes but with thicker walls to deal with municipal water pressure, introduced around 1970. PVC stands for polyvinyl chloride, and it has become a common replacement for metal piping. PVC should be used only for cold water, or for venting. CPVC can be used for hot and cold potable water supply. Connections are made with primers and solvent cements as required by code.
Pipefitters, sometimes simply called fitters, install and maintain pipes that carry chemicals, acids, and gases. These pipes are used mostly in manufacturing, commercial, and industrial settings. Fitters install and repair pipe systems in power plants, as well as heating and cooling systems in large office buildings. Some pipefitters specialize as gasfitters, sprinklerfitters, or steamfitters.
Two-handle faucets are most often found in the bathroom, but you see them in some kitchens. Two-handle faucets use three types of mechanisms. The first two are the same as two of the mechanisms used in a single-handle faucet: cartridge and ceramic disc. The third type is a compression (or reverse-compression) mechanism. Compression faucets are the simplest type, using rubber washers that get compressed against one another to seal the valve. They do tend to wear out faster than other faucet types, but are also least expensive to repair.
Plumbers in Australia have licensing requirements that differ from state to state but it is generally accepted a 4-year apprenticeship with a further minimum experience of 2 years (6 years total) and a further curricular requirement as a benchmark for licensing. Licensed plumbers are also expected to maintain minimum relevant training requirements to maintain their plumbing license