You say that you have only 13 l/min at the taps. What is the flow rate before entering the megaflow? It should be between 20 and 25 l/min. If it is below 20 then that will most likely be your problem. Remember high pressure is not the same as high flow. Just because the pipes are large will it automatically mean that the flow is going to be okay. Have it checked out
Ben, for your first posting you seem to have replied to a discussion which was over two years old!
You dont seem to have fully understood the meaning of dynamic flow rate even though it was referred to earlier in the discussion!
Tony