Tank empties on flush but bowl doesn't empty. eventually only water very slowly empties from bowl. Brand new

replace the flushing controls or install a new cistern

You have cut off water supply and empty tank there are 2 or 3 tank to bowl bolts remove bolts then there is a big nut under tank to bowl gasket undo large nut then install new flush valve,gasket and bolts be sure to install as old one came off.

It may be the wax ring expanded and is restricting the flow.
If you did not install the unit FYI ..the wax ring is inserted between the toilet and the waste pipe to prevent leakage. Sometimes it moves out of place when the toilet gets installed and blocks the flow

Hello. Your toilet is leaking through the flush valve. This is a serious issue as it will use a huge amount of water every day. Check to be sure there is not an obstruction in the tank and if you can not find one, call the plumber. J.

The amount of water in any toilet bowl is determined by its construction and no tank adjustment will ever change that. American Standard has a history of having small water surface areas in their low or ultra low flush toilets. Take a large container of water and pour directly into the bowl. If the ending level remains the same, then that is the manufactured level for your toilet.

Not all tanks completely discharge all of the water when flushed. Measure 1.5 gallons of water into a container. Turn off your water supply to the toilet then flush normally. Replace the water in the tank with your premeasured amount and observe this new water level. You might be surprised to find it is at the same level it always is. Since water weighs more than 8 pounds per gallon, one concept used in todays toilets is to have more than 1.5 gallons of water in the tank and use the extra weight push the water past the flapper at a faster rate while designing the flapper to drop after only 1.5 gallons have passed through.

You are describing a couple of possible problems, neither of which have super easy solutions.
The worst case senario is that there is a crack in the passageway the water travels when it is flushed and just happens to be at a spot that allows the leaky water to go into the floor drain and not on the floor. This is most likely to happen in a brand new toilet situation in which case you take the bowl back to where it was purchased and exchange it.

The most likely scenario however is that there is some form of material caught in the passageway and is "wicking" the water out of the bowl. As water in the bowl disappears from view when you flush, it travels uphill for a moment....over a hump..and then down to continue its journey to the sewer drain. When a piece of material is caught laying over that hump with one end in the bowl water and the other end hanging in empty space, it will draw the water out of the bowl "wick" just like a wick in an oil lamp sucks the oil up through it so the flame continues to burn the oil and not the wick.
Often times just using a plunger vigorously, after a flush and the bowl has refilled, for a couple of minutes will help get the pesky piece over the hump. Otherwise only a special toilet snake (most often called a closet auger) will solve this issue. If you need to get this auger, Do NOT think if it costs more then it must be better. They can range up to $35 or more. You should be able to get this tool, that hopefully you will never have to use again, for between $10 to $15

Wiith all due respect, the Drake toilet is not a regular toilet and doesn't sound the same as a regular toilet when you flush it. It is in the design that allows it use only 1.5 gpf instead of 3.5 gpf. A rather unique thing is that while it is scientifically calibrated to release 1.5 gpf, it does not empty the tank of approximately 1 gallon of water. Therefore if one feels the need for a little extra umph, simply hold down the flush lever when you flush until the tank is emptied.

If bowl is emptying, the most common cause is a crack in the bowl. I have however seen a string get hung in the throat and siphon the water out slowly. May want to pull stool and take a good look. Hope this helps.

The flapper isn't staying open long enought, try holding down the handel for a few seconds each time u flush.

Sounds like your toilet is not vented properly. Possilbly something caught in the trap is causing it to syphon