AMT 3354-070-90 Flapper Valve Assembly, 3" Diaphragm Pump
The AMT 3354-070-90 is the genuine flapper valve assembly for AMT’s 3" diaphragm pumps, listed in the repair parts documentation for the 337 and 338 Series. On a diaphragm pump the flapper valves are not an accessory — they are half the pumping mechanism.
A diaphragm pump works by alternately increasing and decreasing the volume of its chamber. That alone would just slosh liquid back and forth; it is the check valves that turn the motion into flow. On the intake stroke the suction flapper lifts and the discharge flapper is held shut; on the discharge stroke they swap. Every bit of liquid the pump moves passes through these valves twice, and they open and close for every single stroke — thousands of cycles an hour.
That is why a worn flapper is the most common cause of a diaphragm pump that has lost its output. A flap that has hardened, cracked at the hinge, or taken a permanent curl no longer seats cleanly, so part of each stroke is spent pushing liquid backwards through a valve that should be shut. The pump still runs, still sounds normal, and delivers a fraction of what it should. Replace the valves as a set whenever output drops off, and confirm the part number against your parts breakdown before ordering.
Key Features
- Genuine AMT (Gorman-Rupp) service part — assembled to the original specification
- Complete flapper valve assembly, not just the rubber flap
- For AMT 3" diaphragm pumps in the 337 and 338 Series
- Restores output lost to a flap that has hardened, cracked or curled
- Direct replacement — no trimming or fitting required
Applications
- AMT 337 Series diaphragm pumps
- AMT 338 Series diaphragm pumps
- Restoring output on a diaphragm pump that has gone weak
- Replacing a flap that has hardened, cracked at the hinge or curled
- Marine, dockside, sump, dewatering and construction service
Specifications
- Brand: AMT (Gorman-Rupp)
- Manufacturer Part Number: 3354-070-90
- Part Type: Flapper valve assembly (check valve)
- Pump Type: 3" diaphragm pump
- Pump Series: AMT 337 / 338
- Service Note: Wear item — replace as a set when output drops
- Condition: New
Not sure this is the right part? Send us a Picture of the pump plate on your pump and the CLR Marine team will confirm the correct part before you order.
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