I have a 4 qt bag and I filled it full. I measured the amount it holds. I will hold 4 quarts and 20 oz. So I fill it full, If I can take the 4 quarts I love the feeling of fullness. Now and then I get the whole bag, all 4 qts and 20 oz, but that usually doesn't happen.
I start with about 2 quarts, then the next fill is about 3 quarts. I like the fullness of 4 quarts, yet somedays, 3 quarts is all I can handle.
What works best is if I start with some form of laxative before I start. I fast for about 12 hours, taking the laxative after about 4 hours. I usually use 4 to 6 ducolax tablets, but I want to try 4 tables with a good dose of epsom salt with them. That should start rather quickly. After all that is through me, then start with a good enema, running as much water as I can hold the first time. I am going to have to try some J&J bath and body wash to start with one time to see how it works, then water rinses. That way I know I will be really clean.
4 quarts is the goal, if I achieve it fine, if not, then there is always another day.
I used to be able to hold a lot more, seems my capacity has shrunk over the last couple of years. 4 qts still feels really good. Nice and full, great feeling being so full, still being able to hold it and to enjoy the fullness. I have found that warmer water is better, seems like it helps stretch my insides and I can tell where the water is.