What is the maximum horizontal spacing for supporting cast-iron pipe?

The maximum horizontal spacing for supporting cast-iron pipe is indeed 5 feet. This standard is in place to ensure that the weight of the pipe and any fluid it contains is adequately supported, preventing sagging and potential stress on joints and fittings. Proper support also minimizes the risk of leaks and structural failure in the plumbing system.

Supporting cast-iron pipes at intervals greater than 5 feet could lead to excessive bending and stress, which are detrimental to both the integrity of the pipe and the efficiency of the plumbing system. Therefore, 5 feet is established as a maximum to ensure adequate support and maintain the overall reliability of the plumbing installation.