Originally Posted by
merlinrkd
The stem was completely under water in the sink. Neve saw a bubble. That was fully inflated inside the tire.
At 2 psi loss per day the bubble will form very slowly, teeny tiny and pretty much invisible. The bubble will stick to the tube and when it gets large enough it will break away and go upwards.
You can put your hands in and get a death grip on the entire tube, wait for the water to settle and squeeze and you might get an idea of where the leak is. But do you really want to chase this?