What does installing a check valve near the house shutoff valve create?

Installing a check valve near the house shutoff valve creates a closed water system. The primary function of a check valve is to allow fluid to flow in one direction only, preventing backflow. By placing the check valve at this strategic location, it ensures that any water that has already entered the piping system remains trapped within it and cannot flow back out when the water supply is stopped or reduced.

This setup is essential for maintaining consistent pressure within the plumbing system, which is important for efficient operation of fixtures and appliances within the house. It also aids in preventing contamination of the potable water supply, as it stops any stagnant water that could potentially backflow from external sources.

In contrast, an open water system would allow for free movement of water both in and out of the supply lines, leading to potential contamination and pressure issues. A pressure system specifically refers to the conditions within the closed system but doesn't fully capture the primary function of a check valve. A drainage system, on the other hand, pertains to the removal of waste water rather than management of incoming water supply. Thus, the installation of a check valve effectively establishes a closed water system, preserving the integrity and safety of the plumbing network.