We have 4 Toilets - all Mansfield 160's.

In ONLY ONE there is a Black Scum in places and some of this scum floats off when we flush.
Where it is stuck on parts, it is hard to remove.

This one toilet is used less frequency then others.

Does anyone know what this may be and how to correct the problem from occurring ?

Name:  Toiklet1_G.gif
Views: 171
Size:  20.1 KBName:  Toiklet2_G.gif
Views: 177
Size:  19.6 KB