Pentair Diffuser O-Ring for Dynamo

The Pentair 354634 is the diffuser bracket O-ring for the Dynamo aboveground swimming pool pump. It is also carried under the reference O-453, and it is listed at 3/16 in.

What it seals

The diffuser sits over the impeller and directs water into the volute. The O-ring around its bracket keeps that path sealed. When the O-ring hardens, flattens or cracks, water short circuits inside the pump and air finds its way in with it.

The symptoms

A Dynamo that primes slowly, loses prime after it shuts off, or runs with air riding in the strainer pot is often pointing at a seal this small. It is worth checking before you go looking for a cracked housing or a suction line leak.

While you are in there

Do not reuse an old O-ring once the pump is open. The mechanical seal assembly and the strainer pot lid O-ring are the parts most often changed in the same service, and all three are inexpensive next to a second teardown.