Adjust toilet flush

No doubt, this question has been asked and answered previously but I did not see it. My husband just finished installing a new Toto Drake toilet. All went well but we cannot get the flush adjusted. The tank does not empty completely - the flapper closes too soon. He has repeatedly adjusted the chain, shortening the slack as suggested. If he takes up any more, it won't reach. Any suggestions on what else to do? We are assuming the the tank is supposed to pretty much empty of water when flushing. Maybe not??? Thanks, Sharon

The tank only uses a little of the water.
They come factory adjusted.

Just to expand a little on Terry's answer. There is a r********* curve when one switches from the old style toilets to a new low flow. They do not use all of the water in the tank for a regular flush. The "extra" water has 2 functions. The first is the additional depth increases the pressure of the flush. You can use all of the water for a single flush if you have an extra large load just by holding the handle up for a couple of seconds. This feature is rarely needed and it does mean the low flow concept is somewhat defeated in those situations. We have to learn that with a properly designed toilet such as the Toto, a large volume of water is not required for a good flushing action. You should put the flapper chain back to the original position and give the toilet a chance to do what it is designed to do.

Ah Ha

I did wonder about that but unfortunately, literature does not say anything about that. Now, can we remember original setting??? Thank you for your help. Sharon

When the flapper is seated, the chain should be tight. Not so tight as to hold the flapper open, but no play in it.