Factorio Forums

Pipes with between 0.001 and 0.001333 units of fluid does not flow.
This blocks other types of fluid from being able to flow past, severely increasing the likelihood any multifluid pipe setups deadlock.

command used to reproduce Any liquid less than 0.001 gets deleted and I would expect the liquid to spread and get deleted since it would be less than the threshold.
an alternative solution would be to change the threshold for when liquids gets deleted from 0.001 -> 0.00134 or allow for other fluids to override liquids less than 0.00134

Unfortunately i am not considering this to be a bug. Mixing fluids is generally not supported so this corner case is not interesting to handle. If you manage to mix fluids, you can always click a pipe and flush fluids. As you already noticed, there is a threshold of 0.001 for the fluid amount inside of FluidBox under which a fluid will get deleted, the same threshold is also used when fluid is transferred and if flow in a given tick is below this amount, the flow will not happen. Making volume threshold different than flow threshold maybe could fix your specific issue but that would be a hardcoded fix that would only fix the issue for a certain range of fluid box volumes as increasing fluid box area will make the same volume of fluid to have smaller height and as such resulting in a smaller flow when the volumes of both fluidbox would be the same.