You should try to let them have a wet/dry cycle of some kind, the pot should feel lighter before you water again. Definitely don't keep the soil saturated. If you constantly water your pH will always be low.
In my personal experience runoff is never very accurate, and the solutions can be out too. Even a cheap soil pH meter is better imho.
Not sure if you are aware of this but I'll post it anyway, esp if you plan to keep using run-off tests,
Rough Calculation Guide:
Here's some good info on ph.....
If your runoff pH is higher than your starting pH, use this equation to determine your soil pH:*
Soil pH = Runoff pH + Difference
If your runoff pH is lower than your starting pH, us this equation:
Soil pH = Runoff pH - Difference.
For example, say your the starting pH of your solution before it goes in is 6.5 and the pH of your runoff is 7.0. The difference is +0.5, so using the above equation:
Soil pH = 7.0 + 0.5*
Soil pH = 7.5
If your starting pH is 6.5 and your runoff is 6.0, your difference is -0.5 and using the above equation:
Soil pH = 6.0 - 0.5
Soil pH = 5.5
hope that helps,
Dazed..