first of all, i hope google translate is good enough.
A. i build a pump with pipe for 4000 kg water, and i lost about 2% water after it's done.
B. then i replace 1 grid of pipe with a pipe bridge, nothing else is changed. i lost about 30%.
C. then i replace the pipe bridge back with pipe ,anything is the same with A. but i still lost 30%.
D. i tried different ways to dodge the grids one by one, which were the intake, mid, and output points. i always lost 30% water if the pipe go through the grid, which is or was the output point of a pipe bridge, and lost 2% with all other ways. i tried more pipe bridge out point on one pipe line, still lost 30%.
E. if a liquid pipe line lose 2%, then i put a output point of a pipe bridge on the line, keep the intake point free in vacuum (no liquid throuth the bridge), the lost will incrase to 30%, and will not decrease after the pipe bridge is removed.
so there is a bug:
if a liquid pipe line with 1 single pump and 1 single vent go through some grids, and atleast 1 of the grids is or was a output point of a liquid bridge, the liquid through the pipe line will lose about 30%.
F. if the bug is caused by a output point, which was on the pipeline (already removed), the bug will be fixed by a save/load.
G. i tried water supply system with more pumps, bridges and vents, the lost will be about 2%-30%. it is very complicated.
H. replace the pipe bridge with a valve/filter, same thing happens.
I. after i deconstract a used liquid/gas pump, there is a bottled liquid/gas falling down. and there is not mass info on the info page of the bottled liquid/gas. i think that may be the lost liquid. but it is unuseable without mass.
try a liquid pipe bridge/valve/filter.