In a one pipe parallel system, how should a fitter install a gravity main to prevent hammer?

In a one-pipe parallel system, pitching the gravity main down towards the return piping is essential to facilitate the proper flow of condensate back to the boiler or heat source. This installation technique prevents water from pooling in sections of the pipe, which can lead to water hammer—a phenomenon caused by the rapid movement of liquid and air in the system when steam or other gases are introduced, creating pressure surges.

By ensuring that the main is pitched downward, gravity assists in keeping the condensate flowing smoothly toward the return piping, minimizing the risk of obstructions or pressure fluctuations that can exacerbate hammering effects. Proper slope encourages efficient drainage of condensates, which is critical in maintaining system performance and longevity.

When considering other options, installing horizontal piping throughout may lead to stagnation of the condensate, while pitching the main up towards the return can cause water to collect and create pressure issues. Connecting the main to a pressure relief valve does not address the root cause of condensation issues and will not prevent hammer from occurring in the piping system. Thus, correctly pitching the main down towards the return piping is the best practice for preventing hammer in this context.