3 way kitchen tap mixer (hot/cold/filtered) - how do they work? How to fix?

[ClockPie]

Hi

Got a 3 way kitchen tap that looks similar to the image below, but isn't that make. It seems to be a generic type of make branded by 1001 unknown brands. Mine has a collet at the base of the spout to do up/undo. On Amazon on this review, someone has a video of the issue

So what should happen, is the filter tap makes filtered water come out of the rear nozzle, and the hot/cold mix comes out of the front.

After 4-5 years, What is happening, is filtered water comes out of the rear spout and drips from the front; and normal hot/cold comes out of the front but drips at the back.

I would simply swap it, but reading 1001 reviews all models seem prone to this fault. So swapping and the hassle of swapping for it to appear again will be annoying.

How do they work internally in the spout to separate the flow? Is there a pipe from the base for the filtered tap and the hot/cold just go up the spout? Is is possible to remove spout and fix? I've not been able to see any pics of disassembled taps to figure it out, and I'm not wanting to rip ours apart and check just in case it can't be repaired and cant be reassembed!

(I believe the collect at the bottom would unscrew and the spout would pull up - but what is inside is yet unknown)

Thanks

 

[ClockPie]

Hmmm
After shouting at it, the thing has worked perfectly for the last 2 days..... Very odd.
But the question stands, I'm sure it'll revert to playing up at somepoint!