Plumbing – Toilet will not flush and has Air Bubbles

There is a clog downstream from both of these drains. If they are both at the lowest level of the house and you have a septic system, then it's conceivable that the problem is there, but you'd also see water backing up into that bathroom when you run any other showers/toilets in the house.

Most likely, the clog is in the joint in the drain lines where the shower and toilet join on their way out of the bathroom. Get a snake to fish down the drain (probably best to do this in the shower to avoid damaging the toilet bowl) and expect to go down quite a few feet before you reach the problem.

Edit: Revisiting this question, I'd agree that there's also a likely vent blockage from the bubbling descriptions. But the fact that toilet water backs up into the shower points to a drain blockage, too, and that will be easier to fix.

Actually, that's how a toilet is supposed to work.

You can simulate a flush simply by dropping a couple gallons of water in right away.

The spray paint fill is the natural water level. Flushing occurs by suddenly dumping excess water in the bowl. This raises the water level at the back, an a siphon effect comes into play with pulls the remaining water out of the bowl, giving the typical whirlpool effect.

If you're not getting the whirlpool, and a clearing flush, there are two possible scenarios.

1. The tank isn't full, and not enough water is coming down to clear the bowl
2. There is a small blockage in the drain.

But timing isn't an issue.