PVC pipes, widely used for plumbing due to their durability and resistance to corrosion, are nonetheless susceptible to bursting if water inside them freezes. When water freezes, it expands by approximately 9%, exerting significant pressure inside the pipe. While PVC is somewhat flexible and more resistant to freezing temperatures than metal pipes, it has its limits. Continuous freezing and thawing cycles can weaken the structure of PVC pipes, leading to cracks or bursts, especially at joints or places where the pipe wall is thinner or weaker. To prevent freezing, it's advisable to insulate pipes in vulnerable areas, such as basements, attics, and outside walls, and to keep a small trickle of water flowing during extreme cold snaps to prevent ice formation.

Disposing of washed-out emulsion, commonly used in screen printing, requires careful consideration to environmental impact and local disposal regulations. Typically, emulsion waste is considered non-toxic but can cause plumbing issues if not handled properly. The best practice is to first check with local waste management meities for guidelines on disposing of chemicals. Some areas require taking it to a hazardous waste facility, while others may permit it to be solidified (by mixing with kitty litter or a similar absorbent material) and disposed of in regular trash. Importantly, never pour emulsion down the drain without checking if your water treatment facility can handle it, as it could harm water quality or infrastructure. Additionally, investing in a filtration system for your washout booth can capture emulsion particles, reducing waste and making disposal easier and more environmentally friendly.

The question "What amino acid is A?" is slightly ambiguous without further context. In biochemistry, amino acids are often denoted by single letters in protein sequences, but no amino acid is specifically represented by the letter "A." However, if "A" refers to the single-letter code in the context of amino acids, then it stands for Alanine, which is a nonpolar, aliphatic amino acid. Alanine plays a crucial role in glucose-alanine cycles between tissues and liver. Additionally, Alanine is pivotal in protein structure due to its ability to fit into hydrophobic areas. To precisely answer this, additional context on whether "A" refers to its role in genetic coding or biochemical properties would be needed.