I think @saddlebum and/or @Marcarl can defend their own selves on this one but I do not believe the water finding its way to the bottom of the bowl is dependent upon pressure above ambient or vacuum for that matter so yes,, I agree @Patch , the 15 psi thingy is totally not relevant IMHO.. From that I would suggest just taking a small clear jar, fill it 1/2 full of gas, then take some coolant or just water and drip some into it and watch what happens. Once you notice the water collecting in the bottom take the jar and shake it,, after you do I have a gut feeling that the water will be gone as it mixes with the fuel BUT, if you let it sit the water will probably seperate and collect again at the bottom. Now add more water and keep adding water, over a short time I theorize that you will end up with full jar of water and no fuel present. Now if you keep adding water it will over flow the jar, which is what I am thinking Bum has been suggesting was the issue with Pops carb that ended up leaking water out of the overflow tube up on the frame that made it look like the frame was leaking coolant LOL.. If you are wondering if it would be possible for water to leak into the bowl thru the jets maybe you could take a piece of saran wrap. poke a few small holes in it to simulate the jets, put a rubber band around it so the saran wrap is held above the fuel in the jar, pour water across the saran wrap and see if the water will drip into the gas and if it does, keep watering it and see if it will fill the jar. Now lets see what the real guru's think...