Logged out of my server last night and when I logged back in my mechanical pipes had stopped pulling brine from the solar evaporation valve. last night it functioned fine.

EDIT: added picture

Replacing the mechanical pipe at the valve resulted in similar issue to issue #2654

I also had this issue yesterday on singleplayer after I updated from forge 1291 to forge 1395 without updating Mekanism to the build for forge after the fluid registry rework. This could also be your problem, having a Mekanism version that is not compatible with your forge.

Forge Version: 10.13.3.1403
Mekanism version: 8.1.2

@XFactHD there was no mod update I just stopped playing for the evening and came back.

having the same issue

Keeping the area loaded (chunk loader or player) has stopped all occurrence of this bug. This indicates that the bug may be due to how the conductive objects are loaded when a chunk is loaded.

@drunksob for now try chunkloading the area

This should be fixed for the next minor release - the capacity was not being reset on world load.