Which of the following is NOT a sign of a sewer backup?

Brightly colored bathroom tiles are not a sign of a sewer backup because their color and appearance do not indicate any plumbing issues or potential blockages in the sewer system. Instead, brightly colored tiles are simply an aesthetic choice for bathroom design and do not provide any information regarding the functionality of the drainage system.

In contrast, gurgling from drains, slow draining fixtures, and unusual odors from toilets are important indicators that can suggest a sewer backup. Gurgling noises typically occur when air is trapped in plumbing due to blockages, leading to inefficient drainage. Slow-draining fixtures can signify an obstruction that is preventing normal water flow, and unusual odors from toilets may indicate that sewer gases are backing up into the home due to a blockage in the sewer line. Understanding these signs can help in identifying potential plumbing issues before they become more serious problems.