The pre-filter lid nut ESPA Silen (new type, from 2007) is a plastic screw nut that fastens the transparent sight-glass lid onto the body of the pump pre-filter.
A correctly tightened nut ensures a hermetic seal of the pre-filter lid and prevents water from leaking out or air from entering the suction side of the pump.
A damaged or over-tightened nut thread means the lid cannot be sufficiently tightened, which causes water leaks and a drop in the suction performance of the pump.
Replacement is quick and trouble-free – the old nut is unscrewed, the new one is fitted and reasonably hand-tightened with the supplied seal.
The original part for the new ESPA Silen type (from 2007) is fully compatible with the current pre-filter design and the lid of the same generation.
