Water in the toilet bowl is emptying after a minute. I just changed to a higher toilet (16.75) for an elderly resident. I have three other toilets without this problem. I have tried adjusting water in tank and have checked for leaks. How can I fix this?
The water in the toilet seeks the level of the highest level of the high level of the trap, so if you raise the toilet bowl you must raise the trap the same distance. The trap is the curly, s-shaped part of the drain between the exit tube of the bowl and the wall. The highest level of the trap follows the line of bottom of the inner circumference of the trap where the the direction of the flushing water is parallel to the trap, as it is coming out of the climb from the bottom of the trap.
It could also be a vacuum in the drain sucking the fluid back into the drain if there is not a vent pipe running vertically from the drain to the roof to equalize the presscure.
I am not a plumber nor an engineer but a do it yourself person with a little math understanding from American public schools and a very basic, traditional grasp of physical science from experience and from the instruction of a peculiarly motivated chemistry professor at Bakersfield College, Ca USA.
You are probably missing a vent in the drain line. The vents prevents the sewer line from acting as a siphon and emptying the bowl.
Modern toilets use the inside of the bowl as a siphon to pull the waste down, but the siphon must be broken at the exit of the bowl.
Older toilets relied on the force and pressure of the incoming water to push waste down, they did not make a good siphon seal.
Either your bowl refill hose is disconnected or the sewer vent is obstructed.
The refill hose provides water to refill the bowl after the flapper valve has shut. It typically sprays into the tank overflow tube but can also be integrated into the flush mechanism.
If the bowl is properly refilling after a flush, you should suspect a vent problem. If the toilet trap is siphoning dry, probably some sink traps are too. That lets nasty and actually toxic gasses into your house, which you might smell around the sink. If you hear a gurgle at the finish of the sink draining a lot of water (like a mini toilet flush), your vent is almost surely blocked.
Vent pipes are typically seen on rooftops and can be cleared with a sewer snake or garden hose hydrojet. Rarely, a device called an air admittance valve (AAV) is used in place of a rooftop vent, and you may need a contractor to help fix that if it's not accessible.