Quote from EurypteriD
Or instead of the aqueous accumulator use the pumps from mekanism together with the pipes from mekanism. on a 3x3 you can have 5 pumps running meaning 5000 mb water in the system pr sec. Just scale it up.
The mechanial pipes are awesome i use them for all liquid transport (i also have TE3 installed and BC but Meckanism's pipes takes the glory)
There was an update on his twitter
apologies for the late response. I had not discovered the issue until later when building my big reactor for steam. Mekanism pipes have a flow rate limit of 520mb and ducts are 360mb. I had originally gone with mekanism pipes on the accumulators and they always looked filled. I chose accumulators because i didn't want to provide power as well as plumbing. That sad, by the time i got around to Transfer Nodes and upgrades for them my vast network of accumulators were already functional.