Remove pandas data between two points

Question

I have a dataframe of tank level, which can be quite noisy.

I have written an algorithm to (accurately & consistently!) detect peaks and troughs and I now need to remove data on one (filling) part of the cycle, between the grey points and orange points in the image below:

Thanks to @piterbarg and @richardec, I can recognize the next peak following a trough but now I am stuck on how to remove the data between the two (including the High Peak) (colored red below) to only perform further calculations when the level is dropping:

A csv copy of the dataframe is on GitHub. The full data set is > 2M rows, so row-wise calculations are out of the question!

I am completely stuck just now so any help is gratefully received!