I recently purchased a house which was built in 1993. All of the plumbing fixtures are original. Every toilet in the house only holds about 2 to 3 cups of water in the bowl. I have verified the fill valve and tube are functioning correctly. I have also taken a bucket of water and slowly tried to fill the bowl and the level never goes any higher. Same with all three in the house. This is an elongated bowl so there is dry land toward the front, as you can imagine this can be disgusting. Is there anything I can do other than rip them out. If that is the only option, what specification should I look for that determines what the water level in the bowl will be?

Thanks
Joe