I've run into this as well. Here in the US most of us label our pipes simply as "UP", "DN" and "UP AND DN", which I'm guessing is roughly analogous to your "FLL" and "THL" (Just curious, what do these acronyms stand for?) Just like you, my problem was that if I tag a pipe drop as "6" DN" and store the "DN" in a parameter inside the pipe, then that same pipe on the floor below will also tag as "6" DN", when it needs to be "6" UP". It's all subjective: one floor's "up" is another floor's "down."

What I ended up doing was handing the UP, DN, and UP & DN as Label Suffixes in the Pipe Tag Family. My Pipe Tag family has following Types. Each one has a Label dedicated to it, whose visibility is set to a Yes/No Parameter with a name that matches the name of each Type. Think of it as a matrix of Types vs. Yes/No Parameters, in which each Type has only one Yes/No Parameter checked. The labels, all 15 of them, are stacked on top of each other, but only one will be visible in the model depending on what Type is selected.

EX [pipe size]
EX [pipe size] [system abbreviation]
EX [pipe size] [system abbreviation] UP
EX [pipe size] [system abbreviation] DN
EX [pipe size] [system abbreviation] UP & DN

RX [pipe size]
RX [pipe size] [system abbreviation]
RX [pipe size] [system abbreviation] UP
RX [pipe size] [system abbreviation] DN
RX [pipe size] [system abbreviation] UP & DN

[pipe size]
[pipe size] [system abbreviation]
[pipe size] [system abbreviation] UP
[pipe size] [system abbreviation] DN
[pipe size] [system abbreviation] UP & DN

In this case, "RX" prefix stands for Remove Existing, which we use for Demolition Sheets. "EX" stands for Existing, and the third set of Types is for New piping. This isn't a perfect solution, as it forces the user to select the correct Type in each case, but it's the best solution I could come up with, and it's better than hand-writing this stuff in text, which is what people were doing before I created this Pipe Tag family.

Hope that helps!

Another options is to tag the pipes size/abbrv. only. Use a separate text note to describe the levels/direction.

Thanks for the reply guys, I guess separate tags for each version is the way to go.

It is still automating a little bit and keeping sizes updated, so it isn't quite as dumb as stand alone text notes.

FLL THL would mean From Low Level To High Level. We use FA (From Above) TB (To Below) for switching between floors. I've also seen FFA (From Floor Above) TFB To (Floor Below) used at times as well.

The problem with those separate text notes is that if you move the pipe, or delete it, you run the risk of creating a graphical error, i.e. that text note will be pointing to nothing. If the UP/DN/TFB/FFA/WTF/BBQ is stored in the Tag, then it moves and/or deletes along with the thing it's tagging. CAD think vs. BIM think.

In the Netherlands the old cad standard is to show arrows pointing up or down, so we use tags with these symbols in.
To speed things up I made a program that checks if a pipe/duct is vertical (Start and end points have the same X,Y coords) and then sets a "Is Vertical" yes/no parameter. Then you can filter a view with that parameter to show only vertical pipes and tag them with tag all. Only you still have to go around and set what is to/from above and what is to/from below.
It would be nice if there was a way to get the flow direction from each pipe automatically but Ive not found a good method yet, the 'direction' of the pipe itself is just the way it was drawn. I guess it would be possible to check if a pipe crosses the level above or below too.

And seriously...dont use text. If its not attached to an element, and its not reading the data it shows from that element, its a non-bim manual solution that will cost you more time in the long run.

Personally I let the pipe drop/rise symbol speak for itself and if the pipe shows up on the other sheet(s) is enough to tell the reader what is going on. Tag the size and abbreviation of the vertical element and be done. Properly aligning the floor plans between the sheets goes a long way in assisting the reader as they flip the sheets / PDFs.

I would argue that adding narrative text within a tag has very little to do with being "BIM". ;P It's a matter of convenience in the eye of the user.

Thanks for sharing the script josephpeel. That could come in handy.