Disconnect the output line from your pump at the input side to your membrane vessel. Run the line into a five gallon bucket marked at one gallon intervals. Time how long it takes to make two gallons and check that against how much GPM your pump is supposed to produce by doing the math. If you are getting the correct amount of flow your membrane is clogged. Cleaning
a membrane is practically worthless, especially if it sat unpickled for seven months. Leaving a unit in salt water
for seven months not only fouls the membranes but corrodes many of the internal parts
. In an oxygen deprived area such as the internal components of a watermaker
water becomes highly corrosive if left there for long especially to Cat type plunger pumps. When you get your WM working always fresh water flush it after each use and every 5-7 days in between if you are not using it. If you intend to leave it for longer periods un-used store it preferably with Propylene Glycol. Though most WM come with powdered pickling solutions they are more acidic to a membrane and store for half the time the more gentle Propylene Glycol will.