the hoses must not have any bends upwards or downwards. the pump is definitely not strong enough to suck the water up from, for example, 50cm below the drippers... however, if you place the water tank at a height above the drippers in the pots, you will notice that the water tank, even when the pump is off, gets completely drained (suction lift effect) - but this can be prevented with a check valve. Alternative: keep the water level in the tank at about the level of the drippers and use a T-splitter directly at the surface, which is placed approximately at the water surface of the tank, with #1 hose going to the drippers and #2 hose kept very short and letting it drain back into the tank (this will definitely prevent the suction lift effect). Another alternative: buy a pump that actually mechanically closes the pump - this way no water can flow back...
I had exactly the same problem and solved it this way.