well Brick Top I Am not sure I know what you mean by a pour through test...
Are you talking about flushing plan 6.5 water for example and find out what is the run off really is? after 5 gallons or so...
You want to test the runoff of fully saturated soil. You water as usual and allow the soil to drain, but still be fully saturated, and then roughly 15 to 20 minutes later you then water again using distilled water .. allow it about 15 or 20 minutes to drain and then test that runoff. It will give you a more accurate reading for pH and EC.
Another way to do it is to take soil samples. You mix the soil sample with distilled water thoroughly by swirling in a clean jar and then allow it to stand for 30 minutes. After 30 minutes you pour the mixture through a funnel with a coffee filter in it (using two filters put together best). You collect the filtered water in another clean jar. Your water extract is then ready to test for pH and EC. Naturally you would want to make sure that you have a properly calibrated tester/pen before testing. Then pour enough water extract into a clean cup or another clean jar so that the sensor of the tester/pen will be completely immersed in the extract. The tester/pen should be swirled in the water extract to dislodge any air bubbles and then leave the pen still until a stable (unchanging) reading appears. The stable pH and or EC reading is your result.
Those are the ways you find the most accurate readings for what is going on in your soil. Other ways can fool you, things can be missed, inaccurate readings can be the result and you think everything is cool and the gang when it really isn't.