Maytronics Dolphin Supreme M5 double check valve (non-return flap) - 9980891

Maytronics Dolphin Supreme M5 double check valve (non-return flap)

This is the genuine Maytronics double check valve — also known as the non-return flap — that seats inside the filter intake housing on the Dolphin Supreme M5. It functions as a one-way valve: it opens during the cleaning cycle to allow debris-laden water into the filter basket, then closes to lock collected debris inside when the robot pauses or is lifted from the pool.

What this double check valve does in the Dolphin

The flap prevents backflow through the filter intake, maintaining suction consistency across the cleaning cycle. When the pump stops or the robot breaks the water surface, the flap seats against the intake opening under the pressure difference, stopping leaves, sand, and fine grit from re-entering the pool. Without a functional flap, debris falls back into the water the moment you lift the robot.

Which Dolphin models it fits

Part 9980891 fits a wide family of Dolphin robotic cleaners. Confirmed compatible models include the Supreme M4 (2010), Supreme M5 (2010), Supreme M5 Liberty, Wave 60, Wave 65, Wave 80, Wave 90, M400, M500, Bio, C3, C4, C3 Dynamic, Triton Plus, Liberty, Sigma, Odyssey, Nautilus CC Plus, Aquarius XL, and Oasis Z5/Z5i. Always compare the shape of the existing flap in your filter basket housing before ordering — the intake geometry must match.

Signs it needs replacing

The clearest symptom is debris falling back into the pool as you lift the robot out of the water. Inspect the flap directly: a flap that is warped, torn, permanently stiff from chlorine exposure, or no longer sits flush against the intake opening will not seal and must be replaced. Do not attempt to run a cleaning cycle with a missing or cracked flap — the robot will complete the cycle but the basket will be partly empty on retrieval.

How to install it

Open the filter access hatch, remove the filter basket or cartridge, and locate the intake port where the old flap seats. Peel or unclip the worn flap, seat the new one in the same orientation — the hinge edge goes against the fixed locating rib — and close the basket. No tools required; the entire swap takes under five minutes. Run a short test cycle immediately to confirm the flap seals correctly on retrieval.