The salt/sea water pump kept pumping and using power, at 10000L/h, straight into the purification plant. Even though the purification plant couldn't pump out clean water as the tank was full.
It wouldn't bother me except it is using power. I can see the saltwater pipe reporting flow and the clean water pipe stopped.
What weirder I know the saltwater pumps won't pump if no room as originally I had hooked up 2 to one purification plant not realising its a 1:1 ratio. Only one pump would pump as there was no space for more.