Fluval FX4/FX5/FX6 Filter Lid Oring
Pack size
Single O-ring
Fits
FX4, FX5, FX6
Part no.
A20210
Fluval FX4/FX5/FX6 Filter Lid Oring
A worn lid seal is the single most common cause of a leaking FX canister. This is the genuine replacement O-ring for the top cover of the Fluval FX4, FX5 and FX6 canister filters (Fluval part A20210, also cross-referenced under Fluval's earlier codes A214, A218 and A219).
The lid O-ring is what keeps the FX canister sealed under pressure while it's running. It's a simple, inexpensive part, but it's also the first thing worth checking if you notice a slow weep around the top cover, a hiss on startup, or the filter losing prime.
Key features
- Genuine Fluval part – sized precisely to the FX4/FX5/FX6 lid groove, so it seals correctly first time.
- Restores a leak-free seal – the fix for a weeping or hissing lid on an otherwise healthy filter.
- Cheap insurance – worth keeping a spare on hand rather than running an old, compressed or nicked O-ring.
- Quick swap – a five-minute job during a normal filter service.
Will it fit my filter?
Fluval part number A20210 (also listed under Fluval's earlier reference codes A214, A218 and A219). Fits the Fluval FX4, FX5 and FX6 canister filter lids. It does not fit the FX2, which uses a different lid O-ring. Check the model printed on your filter's motor head before ordering.
Specifications
| Genuine part number | A20210 (also A214 / A218 / A219) |
|---|---|
| Fits | Fluval FX4, FX5, FX6 – lid seal only |
| Sold as | Single O-ring |
Suitable for, and not suitable for
Suitable for any FX4, FX5 or FX6 owner dealing with a weeping lid, a startup hiss, or doing preventative maintenance on an older filter. Not suitable for the FX2 or for any leak that isn't coming from the top cover – check hose connections and the AquaStop valve separately if the leak is elsewhere.
Care and maintenance
Fluval doesn't publish a fixed replacement interval for this seal – it's a wear item that hardens and loses its seat over years of use, or fails suddenly if nicked during a cover removal. Wipe it clean and check it for flat spots, cracks or grit at every filter service, and lightly seat it back into its groove rather than stretching it.
Goes well with
Worth fitting during the same service as a media change – the Fluval FX4/FX5/FX6 Carbon Pads or Fluval FX4/FX5/FX6 Foam 3 Pack, since the lid is already off.
Warranty and delivery
Covered by Fluval's standard replacement-parts warranty against manufacturing defects, in addition to your rights under Australian Consumer Law. Standard freight.
Common questions
My filter is hissing on startup – is this the part I need?
A hiss or slow weep around the top cover is the classic symptom of a worn or nicked lid O-ring, so yes, this is usually the fix. If the noise is coming from the hoses or the AquaStop valve instead, this part won't resolve it.
Does this fit the FX2?
No – the FX2 uses a different lid seal. This part is sized for the FX4, FX5 and FX6 only.
How do I know when to replace it?
Check it at each service for flattening, cracking or grit. There's no fixed Fluval interval – replace it when it's visibly worn or if you're getting a leak or hiss around the lid.
Is this a genuine Fluval part?
Yes – Fluval part A20210 (cross-referenced under A214, A218 and A219), not a generic aftermarket equivalent.
