Background
Prior to doing some research, don’t trust any expert in plumbing service. It’s because the return of the finding after research may be larger than expected. While so-called experts in plumbing telling you to replace the whole set of bath shower mixer, pay attention to other opportunity to save the existing mixer, especially if you’d like to be environmental friendly.
They’ll tell you that no parts is available for the obsolete model. Got 11 so-called quotations from an online experts matching platform, cfumaster.com, none of them provides repair services. Indeed, most of them suggested that there must be replacement of the whole mixer set. Another one called 水道屋, they have a contact person to get requirement and response, but also said no parts available for fixing. However, unnecessary replacement of durable building materials is harmful to our environment. I guess they want to earn you money by providing installation service of a new mixer.
Issue
Water could barely be diverted to the shower after pulling the diverter knob, but aside from this malfunctioning the bath shower mixer is still in good condition.
Solution
Purchase the appropriate diverter from a building material store, Luen Hing Hong Building Materials Ltd. in Portland St., Mongkok. The replace it on my own according to the instruction given by the sales of the store. 
Tricks
- The video footing about replacement of bath/shower diverter for other brands is totally irrelevant to this model Grohe 33485.
- Neither pliers nor adjustable spanner wrench can help to remove the parts as the inside material of the knob is rubber-like material, i.e. not rigid. Only 6 point combination wrench with size 11/16 can do the trick.
