Polaris Zodiac 180 280 380 3900 Backup Valve Mechanism (G53) circuitbreakers The after 2003 model compatibility and The after 2003 model compatibility and quantity of eight format give this set practical value because sand filter internals work best when they match the original model generation and quantity relationship closely This type of pump is especially useful when a bath system needs to be restored with a well recognized line that is easy to support with related LX components and service parts helping the cleaner maintain reliable movement throughout the pool A failing backup valve or related backup valve part can cause the cleaner to stall