In order to exclude condensed water, steam and other water-containing gas pipelines should have a certain slope, generally not less than two thousandths. For underground drainage pipes using gravity flow, the slope shall not be less than 5/1000. Steam or other water-containing gas pipelines are provided with drain pipes or traps at the lowest point, and some gas pipelines are also equipped with gas-water separators to drain water in time to prevent water hammer and block gas flow in the pipes. The water supply or other liquid pipeline is provided with an exhaust device at the highest point to remove the air or other gas accumulated in the pipeline to prevent abnormal operation caused by air resistance.
