Which type of faucet is not permitted for sampling THMs?

Swivel faucets are not permitted for sampling total trihalomethanes (THMs) due to the potential for contamination or inaccurate sampling results they might introduce. The design of swivel faucets allows for the spout to move freely, which can influence the water flow and cause the sample to not accurately represent the water quality, particularly in regard to the concentration of THMs.

In regulated water sampling, consistency and precision are critical to ensure that the collected samples reflect true water quality conditions. The designs of other types of faucets, such as standard, wall-mounted, or commercial-grade faucets, are generally considered more suitable for sampling because they provide a stable outlet for water that can deliver a representative sample without the variables introduced by moving parts. This is crucial in ensuring that samples are taken without risk of skewing the results due to changes in flow patterns or other mechanical factors.