Can an "Essential Series Ball Valve" be used on a Nexus filter?

You cannot screw an "Essential Series Ball Valve" into a ball valve connected to a Nexus Filter. The threads on the collars are different. 

COMPATIBLE WITH NEXUS FILTERS (With pale blue coloured handles)

Ball valves used as the maintenance and waste valves on Nexus have pale blue coloured handles, therefore identical replacement valves must be purchased if you intend to screw new valves onto your existing threaded collars. These valves are available from our dealer network and website: https://evolutionaqua.com/double-union-ball-valves

ESSENTIAL SERIES BALL VALVES (With bright blue coloured handles)

The "Essential Series Ball Vales" with bright blue handles are a cost-effective solution. Whilst not compatible with existing Nexus Filter valves, they can be connected to pipework to isolate equipment, to regulate flow and to help create by-pass systems. If you need to purchase one of these ball valves click here: https://evolutionaqua.com/essential-series-double-union-ball-valves