Astralpool O-ring 151.7 × 6.99 mm for Cantabric, Millennium and compatible side-mount sand filters - 4405010178

Astralpool O-ring 151.7 × 6.99 mm for Cantabric, Millennium and compatible side-mount sand filters

This is the genuine Astralpool toric O-ring measuring 151.7 mm inner diameter by 6.99 mm cross-section, engineered as the primary pressure seal between the filter vessel body and its transparent lid on side-mount sand filter models. Manufactured to tight dimensional tolerances, it maintains a leak-free joint at the filter head across all normal operating pressures. It is a direct OEM replacement that restores the filter to factory specification without modification.

Function and sealing role

The O-ring sits in the machined groove at the mating face of the filter lid and vessel, creating the watertight barrier that keeps pressurised water inside the tank during all multiport valve positions — filtration, backwash, rinse, recirculation and waste. Without an intact seal at this joint, system pressure cannot be maintained and water escapes around the lid, reducing filtration efficiency and potentially causing water loss on the plant-room floor.

Compatible filter models

This O-ring is the lid seal for Astralpool side-mount sand filters in the ~150 mm seating range, confirmed to fit the Cantabric (Ø 400–600 mm vessel, side-mount valve variant with transparent lid) and the Millennium Lateral (side-outlet) series across vessel diameters Ø 380–660 mm. Always cross-reference your filter’s exploded-view diagram to confirm the seating diameter before fitting.

Symptoms that indicate replacement is needed

Visible weeping or steady water leakage from the lid-to-body joint is the clearest sign the O-ring has failed. A progressive drop in filter working pressure, the smell of damp around the filter housing, or a visible flat, cracked or extruded ring on inspection all confirm the seal is no longer serviceable. Because the transparent lid on side-mount Cantabric and Millennium filters allows visual access to the interior, condition of the O-ring groove area can often be checked without full disassembly.

Why genuine Astralpool matters

The 151.7 × 6.99 mm cross-section is a precision dimension; an O-ring even fractionally undersized will not generate enough squeeze to seal under pressure, while an oversized ring risks pinching and tearing during lid closure. Genuine Astralpool elastomer compound is formulated to resist chlorinated and salt-water pool chemistry and UV exposure, maintaining elasticity season after season. Non-genuine aftermarket rings of nominally similar size frequently use inferior compounds that harden, flatten or swell prematurely, reintroducing the leak within one season.

Installation note

Before fitting, clean the O-ring groove and lid mating face thoroughly to remove any debris or old lubricant residue. Apply a thin film of silicone-based O-ring grease to the ring before seating it — never use petroleum-based lubricants, which degrade rubber compounds. Seat the ring evenly around the groove with no twists, then close and lock the lid carefully to avoid pinching.