I just installed a new garbage disposal unit. My problem is my diswasher won't drain while it connected it to it. I disconnected the hose from the disposal and it drain into the sink. What did i miss?

1) Copy following link for garbage disposal troubleshoot:
http://waterheatertimer.org/How-to-repair-and-install-Garbage-disposal.html

2) Remove tubular drain and clean out, so disposal drains.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Remove tubular pipes under sink and clean out disposal.
Copy following links for steps for clogged disposal:
http://waterheatertimer.org/How-to-repair-and-install-Garbage-disposal.html

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

see this causes and proceed according. God bless you
Belt, Water Pump Although few dishwashers have a water pump belt, if the dishwasher won't drain there might be a worn or broken water pump belt. After removing the lower kick panel the motor can be seen in the front, the water pump belt is on the bottom of the motor.

Drain Pump If the dishwasher won't drain, the drain pump might be defective. Test the pump motor with an Ohm meter. Drain pumps are not repairable, if it's defective it will need to be replaced.

Drain Impeller The drain impeller is attached to the pump and pushes the water out of the dishwasher, through the drain tube and into the garbage disposer or drain line. If the dishwasher won't drain, the drain impeller might be broken or worn out. Replace both the impeller and seal at the same time.

Drain Solenoid Kit If the dishwasher won't drain, the drain solenoid kit might need to be replaced. The drain solenoid is an actuator that opens a flap to allow the water to drain.
Drain Valve The drain valve can get clogged with debris and should be cleaned out if the dishwasher won't drain. If it seems clear of debris but won't actuate, it will need to be replaced. The drain valve is not repairable Pump and Motor Assembly If the dishwasher won't drain, the pump and motor assembly might be defective. If the motor runs during the drain cycle, check for a blockage in the drain line. If the motor won't run during the drain cycle or if it just hums when it should be running, the pump and motor assembly might need to be replaced.

Clogged or Improperly Installed Garbage Disposer If the dishwasher won't drain and the garbage disposer was installed recently, the installer might have forgotten to knock out the drain plug from this disposer. All garbage disposers are sold with a solid plug in the drain tube for situations where a dishwasher isn't connected. However, if the dishwasher is connected, the plug will need to be removed. If the disposer wasn't replaced recently, remove the dishwasher drain hose from the disposer and clean out both the fitting on the disposer and the end of the drain hose. These are the most common places to find an obstruction if the dishwasher won't drain.

Clogged or Improperly Installed Garbage Disposer If the dishwasher won't drain and the garbage disposer was installed recently, the installer might have forgotten to knock out the drain plug from this disposer. All garbage disposers are sold with a solid plug in the drain tube for situations where a dishwasher isn't connected. However, if the dishwasher is connected, the plug will need to be removed. If the disposer wasn't replaced recently, remove the dishwasher drain hose from the disposer and clean out both the fitting on the disposer and the end of the drain hose. These are the most common places to find an obstruction if the dishwasher won't drain.

Check Valve If the dishwasher won't drain the check valve might be stuck closed. The check valve is a small plastic device which prevents water from returning to the dishwasher after it has drained. If the valve gets stuck closed, it will prevent the water from draining. The check valve is the device that the drain hose is attached to on the dishwasher.

Check Ball If the dishwasher won't drain the check ball might be stuck. The check ball is a small plastic ball in the check valve which prevents water from returning to the dishwasher after it has drained. If the ball gets stuck, it will prevent the water from draining also. The check valve is the device that the drain hose is attached to on the dishwasher.

New installation? Do you have a garbage disposal, there is a pluged port on the garbage disposal. Is the drain hose free to move, not crushed or twisted, Please provide model name and number.
InMrFixIt

i also found my miele wouldn't drain after replacing a garbage disposal. it turned out I forgot to knock out the plug on the disposal where the diswasher discharges....Doh !....

You are missing that the plug needs to be removed on a new disposer. All new units have this port sealed as not every install will have a diswasher...Take the unit out, and look in the hole, woopsies. Push it out with a screwdriver and a hammer. this blockage would cause the water to come out of the vacuum break on the counter.
Fortunately not a big problem to repair.

Since the drain pump will pump the water out using the "cancel/drain" button, if it did not work then your problem is likely to be in the drain hose system or the garbage disposal downstream from the drain pump. Check for kinks in clogs in the drain hose. Grease can build up in the portion of the drain hose just before it attaches to the garbage disposal.

sound's like you have a problem with your drain pipe's. it is not normal for water to come back up.check the allen key bolt, located on the bottom of unit .insert allen wrench /key,and turn in a clock wise&counter clockwise motion to see if disposal is jammed.you also might consider some drain opener before it get's worse

ur discharge line is to low...try to make a loop

Yes - the dishwasher drains into the disposal - if the disposal is blocked up - it will hamper the dishwasher draining.