Hogsheads per acre fortnight measures volumetric flux, not volumetric flow.
If you know the area of your pipe in the direction of flow in outhouses (that's microbarns for the layman) you can calculate the rate of flow in the standard rundlets per galacticyear in your head with the following simple conversion:
rundlets/galacticyear = (hogsheads/acre fortnight) × 3.5 × (pipe in outhouses / 4.04685642 × 10^37) × (5.85 x 10^9)
(without getting too technical, this is assuming hogsheads of ale, and the lower bound on a galactic year. Of course rundlets always refers to ale and not sherry/tobacco)
So a pipe with an opening of 2.02342821 × 10^34 outhouses (5 cm diameter) and a volumetric flux of 16 hogsheads/acre fortnight has a rate of flow of 163 800 000 rundlets per galactic year.
(or for you scientific types thats 427,417 years, 56 days, 23 hours, 29 minutes and 45.6 seconds per library of congress.)