What is a check valve?

What this means for your home project

1. Observe the sump-pump outlet pipe for a visible blockage or freezing and where it sends water; note whether discharge is directed away from the house. Source: North Dakota State University Extension, read 2026-11-03.
2. Ask the installer which silent check-valve design is proposed for the pump discharge, so the written reply identifies the design. Source: ASHRAE, read 2026-11-03.
3. For a Louisiana job under section 731.B, request a written layout showing the check valve and gate valve between the pump and gravity drainage system. Source: Louisiana Administrative Code via Legal Information Institute, read 2026-11-03.
4. Ask that Louisiana layout to show access above the sump cover, or the removable-cover access pit where the quoted below-grade exception applies. Source: Louisiana Administrative Code via Legal Information Institute, read 2026-11-03.

When and why do I need a check valve?

On a home sump pump, a check valve keeps water in the outlet pipe from returning to the pit after shutdown. North Dakota State University explains that returning water can make the pump cycle unnecessarily and shorten its life. “Either type of pump should have a check valve on the water outlet pipe so water doesn't flow back into the sump when the pump shuts off.” Source: North Dakota State University Extension, read 2026-11-03. “Water flowing back and forth can cause the pump to turn on and off more frequently than necessary, which decreases the life of the pump.” Source: North Dakota State University Extension, read 2026-11-03.

Where should a check valve be located?

For Louisiana sump/ejector piping, section 731.B puts a check valve and a gate valve between the pump and the gravity drainage system. It requires accessible placement above the sump cover, or permits an accessible pit with a removable cover for the stated below-grade ejector arrangement. Ask for a drawing showing both valves and how each will remain accessible. “A check valve and a gate valve shall be installed in the pump or ejector discharge piping between the pump or ejector and the gravity drainage system.” Source: Louisiana Administrative Code via Legal Information Institute, read 2026-11-03. “Such valve shall be accessibly located above the sump cover required by §731. A of this code, or when the discharge pipe from the ejector is below grade(G), the valves may be accessibly located outside the sump below grade(G) in an access pit with removable access cover.” Source: Louisiana Administrative Code via Legal Information Institute, read 2026-11-03.

How do I select a check valve for my sump pump application?

For a sump-pump discharge, ask whether a silent, spring-loaded check valve fits the application. ASHRAE’s 2020 handbook recommends silent checks for pump discharge lines. A swing check uses a hinged disk; the silent design instead uses a spring to close a guided disk rapidly. Request the proposed disk and spring design in the written scope. “Swing check valves have hinge-mounted disks that open and close with flow (Figure 28).” Source: ASHRAE, read 2026-11-03. “In silent or spring-loaded check valves, a spring positively and rapidly closes a guided, floating disk.” Source: ASHRAE, read 2026-11-03. “Silent check valves are recommended for use in pump discharge lines.” Source: ASHRAE, read 2026-11-03.

What is the difference between a backflow preventer and a check valve?

A single check valve controls flow direction; a double-check backflow assembly contains two independently acting, spring-loaded checks. Florida’s drinking-water FAQ describes shutoff valves at both ends and test connections. It limits this assembly to nonhealth hazards, so the assembly’s intended hazard protection belongs in the selection discussion. “A DC is a mechanical backflow preventer that consists of two independently acting, spring-loaded check valves.” Source: Florida Department of Environmental Protection, read 2026-11-03. “It includes shutoff valves at each end of the assembly and is equipped with test cocks.” Source: Florida Department of Environmental Protection, read 2026-11-03. “A DC is effective against backpressure backflow and backsiphonage but should be used to isolate only nonhealth hazards.” Source: Florida Department of Environmental Protection, read 2026-11-03.

Why use an air vent hole in my discharge pipe?

The air vent hole lets trapped air escape from beneath the check valve. In its pump-installation FAQ, the Sump and Sewage Pumps Manufacturers Association describes a pump running without discharging water as a possible symptom when an air vent is absent. “The air vent hole allows air trapped under the check valve to escape.” Source: Sump and Sewage Pumps Manufacturers Association, read 2026-11-03. “A symptom of not having an air vent would be the pump runs but no water is being discharged.” Source: Sump and Sewage Pumps Manufacturers Association, read 2026-11-03.

Sources

• Check Your Sump Pumps Now — North Dakota State University Extension; read 2026-11-03.
• Cross-Connection Control and Backflow Prevention Program FAQ — Florida Department of Environmental Protection; read 2026-11-03.
• 2020 HVAC Systems and Equipment Handbook, Chapter 46: Valves, section 9 — ASHRAE; published 2020; read 2026-11-03.
• Frequently Asked Questions About Pumps and Pump Installations — Sump and Sewage Pumps Manufacturers Association; read 2026-11-03.
• Title 51, Part XIV, section 731: Sumps and Ejectors — Louisiana Administrative Code via Legal Information Institute; published November 2012 (promulgation); read 2026-11-03.