A 90° elbow with a built-in check valve — designed specifically for the waste (drain) port of RO membrane housings. Prevents backflow on the drain line while routing tubing at a clean right angle. 1/8″ MNPT threaded port, 1/4″ OD quick-connect tube side.

What it does

This check elbow fitting does two jobs in one piece: it connects the waste (drain) port of an RO membrane housing (1/8″ MNPT threaded) to 1/4″ OD drain tubing at a 90° angle, and its integrated check valve ensures waste water flows in one direction only — out to the drain, never back toward the membrane.

Without a check valve on the waste line, drain water can back-siphon into the membrane housing under certain pressure conditions, contaminating the purified side. This fitting eliminates that risk. It’s the standard fitting for the waste port on traditional under-sink RO systems.

Key benefits

• ✓Built-in check valve — prevents waste water backflow into the membrane
• ✓1/8″ MNPT × 1/4″ QC — threaded port side, push-fit tube side
• ✓90° elbow — compact routing from the waste port to drain tubing
• ✓Purpose-built for the waste/drain line — not a general-purpose fitting
• ✓Standard on traditional under-sink RO systems
• ✓Automatic quantity discounts starting at 2 units

Specifications

Compatibility

Often used with

Good to know before you buy

• Wrap the threaded end with PTFE (Teflon) tape (2–3 turns clockwise) before threading into the waste port.
• Hand-tighten, then snug slightly. Do not over-torque — the housing is plastic.
• Push 1/4″ OD drain tubing into the quick-connect port until it seats.
• Confirm flow direction: the check valve allows flow FROM the housing TO the drain only. Install so the arrow (if marked) points toward the drain.
• This fitting is waste-line specific — do not use on the purified output side.