Filtermaster SB20 Mechanical Seal

The Filtermaster SB20 takes a mechanical seal for a 3/4″ shaft with carbon / ceramic faces. This aftermarket seal replaces Onga part 700270 and Astral part 75508, and the same seal suits the Filtermaster SB30 and several AstralPool and Onga pumps. Measure the shaft or compare your old seal side by side before fitting.

Filtermaster SB20 seal part numbers

If you have the packet or a parts list for the old seal, look for either of these numbers. This seal is listed as a replacement for both, and it is a 3/4″ shaft seal with carbon / ceramic faces.

• Onga 700270
• Astral 75508

Which pumps use the same seal as the SB20

The SB20 shares this seal with the Filtermaster SB30, the AstralPool CTX, CX180, CX240 and CX280, the Onga Leisuretime LTP1100, and the Onga Pantera PPP750, PPP1100 and PPP1500.

It is also listed for pumps we don’t have a separate page for, including the Filtermaster FM Series and FX Series, Poolquip Filtermaster, Poolquip Hustler and Premier, Poolrite Cougar, Enduro and Quietline, AstralPool BX and TX, and the Waterco Charger. The same seal is sold on its own as our 3/4″ pool pump seal, and parts for other Filtermaster models are grouped on our Filtermaster service kits page.

Signs the SB20 seal is leaking

A mechanical seal works by pressing a spinning face against a fixed seat with a film of water between them. Grit, running dry and plain age wear the faces until water gets through. Replace it promptly, because water that tracks along the shaft can reach the motor bearings.

• Drips or a steady weep where the pump body meets the motor.
• Rust or white scale streaks running down under the motor.
• The pump drawing air at the motor end and struggling to hold prime.

Before you order

Check the old part before fitting: match the size of your old seal.

What seal fits a Filtermaster SB20?

The Filtermaster SB20 uses a mechanical seal for a 3/4″ shaft with carbon / ceramic faces. This seal replaces Onga 700270 and Astral 75508.

What part numbers does the Filtermaster SB20 seal replace?

This aftermarket seal for the Filtermaster SB20 replaces Onga 700270 and Astral 75508. If your old seal carries a different number, compare its shaft size and faces before ordering.

Does the Filtermaster SB30 use the same seal as the SB20?

Yes. The Filtermaster SB30 is listed with the same 3/4″ carbon / ceramic seal as the SB20, and it has its own SB30 seal page.

Can I replace just the seal on a Filtermaster SB20?

Yes. The SB20 seal is sold on its own. If the motor has also been slow to start, the SB20 service kit adds a 30 µF run capacitor for less than buying both separately.

Do I replace both halves of the SB20 seal?

Yes. Always fit the new rotating face and the new stationary seat together on the SB20, because a new face running on an old worn seat will leak again quickly.

What if it doesn't fit?

If you're unsure, send us a photo of your old part and the pump's label before ordering.