bowl losing water

I just moved into a fairly new rental home. It has a couple of Briggs 2-piece toilets with conventional fill valves. Both toilets flush and fill normally, but one of them is somehow losing water from the bowl. After flushing, the bowl refills so that the water spot is normal (about 10 or 12 inches). However, as soon as the valve shuts, the water level in the bowl begins dropping. If you look carefully, you can actually see it recede! After a few minutes, the water level stabilizes at the top of the throat, where the water spot is about 4 inches.

Any idea what could cause this? The bowl is nothing more than a giant trap so it makes no sense to me that it could lose water.

David

If the toilet that looses water, pour a pail of water slowly into that bowl and watch. If water level drops again there is a sand hole leak in the casting that has warn through. probably would need to replace the fixture. If it holds, then look for a plugged vent.

plumber1 said:

If water level drops again there is a sand hole leak in the casting...

Click to expand...

Thanks for the tip. I used a bucket and water dropped again, just as before. Hole must be pretty good sized -- water drops several inches in just a couple of minutes. Presumably it's leaking into the sewer?

According to Briggs website, the toilet has a five-year warranty (house is a couple years old). Are these warranties usually for parts only? I guess it wouldn't hurt to contact the installing plumber to see what he says.

David