De or het waterverversing?

The correct Dutch article is:

de waterverversing

Rule Words ending in -ing: almost always de. See the rule

How to use waterverversing

the waterverversingde waterverversing
this waterverversingdeze waterverversing
that waterverversingdie waterverversing
our waterverversingonze waterverversing
your waterverversingjouw waterverversing
every waterverversingelke waterverversing
which waterverversing?welke waterverversing?
a big waterverversing / the big waterverversingeen grote waterverversing, de grote waterverversing