I've had the same problems with the Salt Water Flush (SWF).
What I've done is experimented around with the amount of salt. The book calls for 2 teaspoons of salt for 1 liter of water. This was producing the same results on me that you are describing... it didn't always happen.
So now I've gone up to 3 teaspoons of salt for one liter of water, and that seems to work just fine.
Some of the other things I do to ensure it passes through:
-I make my 90oz of lemon juice drink right after drinking the SWF. This keeps me standing up.
-I don't lie down. I think this keeps gravity from pulling the SWF (Salt-Water-Flush) through the system?
Usually I am done in an hour or two.
I still wonder if some of the water is being absorbed into my system and what other things I can do to ensure the SWF (Salt-Water-Flush) moves through. Some other thoughts are:
-The time of day it is taken. Early morning may work better?
-How hydrated I am. Drinking more water during the day with the lemon drink?