Fluval 303 Seal Ring 160mm
Water type
Freshwater + Marine
Fits
Fluval 303
Part no.
A15870
Fluval 303 Seal Ring 160mm
A weeping motor head is almost always this ring, not the pump.
This is the genuine Fluval seal ring, part A15870, 160 mm — the main gasket that seals the motor head onto the canister body on a Fluval 303 filter. It's a wear part: it hardens and flattens with age even sitting unused, and a canister that never used to leak can start weeping around the lid seam for no reason other than this ring calling it quits.
Key features
- Genuine Fluval A15870 — sized to the 303's canister rim, not a generic o-ring cut to a similar diameter.
- 160 mm — the main lid seal, a different part from the smaller impeller shaft seal used elsewhere on the same filter.
- Fixes the most common leak point — a chalky, flattened ring is the usual reason a 303 starts weeping, and the fix is a five-minute part swap.
Specifications
| Manufacturer part number | A15870 |
|---|---|
| Size | 160 mm |
| Position | Motor head / lid seal, where the head meets the canister body |
| Sold as | Single ring |
| Water type | Freshwater and marine |
Will it fit my filter?
This is the lid seal for the Fluval 303 canister filter. Fluval's 300-series also included the closely related 403 — we haven't confirmed from Fluval's own documentation that the two share this exact ring size, so check your old ring against this one before ordering rather than assuming.
It does not fit the later 304–307 or 404–407 range, which uses a different motor head and a different seal — see the 304–407 motor seal ring instead.
What's included, and not included
Includes 1 x 160 mm seal ring. Does not include the smaller impeller seal ring, a different part on the same filter.
Suitable for, and not suitable for
Suitable for an older Fluval 303 that's otherwise sound and just needs to stop weeping at the lid. Not suitable for newer Fluval canisters, which use different seals entirely.
Care and maintenance
Check the ring for hardening, flattening or cracking at each service. A light smear of silicone-safe grease makes reseating the head easier and can help the seal last, though it isn't required for the ring to work.
Warranty and delivery
Supplied as a genuine Fluval replacement part. Your rights under the Australian Consumer Law apply in full and nothing here limits them. No separate manufacturer warranty term is quoted on rubber service parts. Ships as a standard small parcel anywhere in Australia.
Common questions
What's the difference between this and the impeller seal?
This 160 mm ring seals the lid to the canister body. The impeller seal is a separate, smaller ring further down in the motor head.
Does this fit the Fluval 403?
Likely, since the 403 shares much of the 303's design, but we can't confirm the exact seal size from Fluval's own documentation. Check your old ring first.
My canister has never leaked before — why is it leaking now?
Rubber seals harden and flatten with age even in storage, so a first leak on an older filter is usually the ring, not new damage.
