22
Aquifer Flow Test
The flow test is the most useful diagnostic test for system performance, and should be done
before replacing or cleaning your membrane. Changes in production or water quality are nor-
mally caused by something
other than
the membrane, unless the system has been left unused
for a long time.
Before the flow test, change the filter and clean the sea strainer. Carefully check for water or
air leaks, as air in the system will cause low production and erratic salinity. Look for air bubbles
in the product flow meter, feed water hoses, and brine overboard hose.
Run the system and watch the pressures very closely. If the feed pressure to the Clark Pump is
asymmetrical from one stroke to another, this could be part of the problem. A difference of a
few PSI is acceptable, but anything over that is an issue. If the pump is asymmetrical, Clark
Pump repairs should be done before continuing with these tests.
If no asymmetry is noted, continue with this test.
Make sure the ShurFlo overpressure cutout switch (PL
-
PMP
-
SFPH) is set to 125 PSI. With the
pump running, close the brine service valve. The feed pressure should rise to 125 PSI, then the
pump should shut off. If the pump shuts off at a lower pressure see
“
SF
-
2 Adjust ShurFlo Pres-
sure Switch,
”
later in this manual.
You will need a graduated bucket and a stopwatch. Measurements must be very accurate, as
errors of just a few percent will skew the results. Log the voltage at the feed pump at the same
time. Confirm at least 12.5 volts at the pump on 12
-
volt systems.
1.
First divert the product flow into the bucket and record how long it takes to accumulate a
given amount. Product flow is usually expressed in Gallons Per Hour or Liters Per Hour, so
it
’
s easiest and most accurate to collect the flow for exactly ten minutes, then multiply the
quantity by six to get GPH or LPH. Alternatively, you can collect exactly one gallon or four
liters then calculate GPH or LPH as follows:
3600/time in seconds x quantity of water=GPH or LPH
There are 3600 seconds in an hour.
Example: It took 9 minutes, 45 seconds to collect 1 gallon of product water, so
3600/585 x 1 = 6.15 GPM (9 times 60 seconds is 540 plus 45 equals 585 seconds).
