Lisnhlin RV Vacuum Breaker Check Valve Replacement 571 — 1/2" NPT, 8–125 PSI

Lisnhlin 571-VAC-CHK-A is a one-way vacuum breaker check valve designed to prevent backflow in RV black tank flushing systems, protecting your freshwater supply and stopping leaks.

This compact replacement check valve fits into the black tank flusher line and is commonly used between the freshwater source and the tank flusher on campers, travel trailers, and motorhomes. Built to handle typical RV water pressure and to replace cracked or leaking OEM parts, the 571 model keeps wastewater contained during flushing and helps maintain clean freshwater connections while on the road.

How does this check valve stop backflow into my RV freshwater system?

The Lisnhlin vacuum breaker check valve operates as a one-way device that allows water to flow toward the black tank flusher while preventing reverse movement. If pressure drops or a downstream fault occurs, the internal mechanism closes to block contaminated water from returning toward your potable supply. It’s an inexpensive safeguard for any RV flush line where cross-contamination would be a problem.

• One-way internal valve design prevents reverse flow.
• Installs between freshwater inlet and tank flusher for direct protection.
• Helps keep potable water lines separate from black tank discharge.

What are the installation requirements and thread size for the 571-VAC-CHK-A?

Installation is straightforward: the part uses 1/2" NPT male threads on both the inlet and outlet and should be threaded into standard RV plumbing fittings. For correct operation it must be mounted at least 6 inches above the highest point of any item connected to the waste tank where the flusher is installed. Follow common plumbing practices—use thread sealant or PTFE tape and hand-tighten with a wrench to avoid overtightening.

• 1/2" NPT male threads on inlet and outlet for common RV fittings.
• Mount at minimum 6" above the highest connected waste-tank point.
• Use PTFE tape or suitable thread sealant; tighten to secure but avoid stripping threads.

What water pressure can this vacuum breaker withstand, and is it durable for travel?

The 571-VAC-CHK-A is designed to tolerate typical RV water pressures, rated to perform reliably between 8 and 125 PSI. Its construction is intended for repeated use in mobile environments, resisting pressure fluctuations and everyday wear. Replacing a worn or cracked check valve with this part restores efficient flushing and reduces the chance of leaks or wet floors in your vehicle.

• Rated working range: 8–125 PSI to suit most RV systems.
• Durable materials resist pressure cycling during travel.
• Direct replacement for cracked, leaking, or faulty check valves.

How will replacing this part improve my black tank flush performance?

A fresh, functioning vacuum breaker ensures water flows only toward the black tank flusher, preventing back-siphonage and the unpleasant side effects of a malfunctioning valve—such as slow flushing, odors, or unexpected leaks. Swapping a degraded valve for the Lisnhlin 571 restores reliable flow control and reduces maintenance needs. It’s a small part that has a big impact on cleanliness and convenience in your sanitation system.

• Stops leaks and prevents wastewater from reaching freshwater lines.
• Restores consistent flushing pressure and flow direction.
• Reduces risk of wet floors or blocked lines caused by failing valves.

Who is this for: RV owners, campers, and fleet technicians who need a dependable, easy-to-install replacement for a faulty black tank flush check valve. If you manage routine RV maintenance or experience leaking or backflow during black tank flushing, the Lisnhlin 571-VAC-CHK-A is a practical upgrade to protect your freshwater lines and keep your sanitation system working as intended.