[1.3.2] TileEntity, PacketHandler, questions

Again having Problems, now try my first Block that can do something!

i have a Block, TileEntity

in the TileEntity want to store something like Water so i make a Variable waterLevel

ItemStack var10 = par5EntityPlayer.inventory.getCurrentItem();
        	
            
            if (var10.itemID == Item.bucketWater.shiftedIndex)
            {
                par5EntityPlayer.inventory.setInventorySlotContents(par5EntityPlayer.inventory.currentItem, new ItemStack(Item.bucketEmpty));
            	  if(waterLevel < 10)
            	  {
            		  waterLevel = 10;	
            	  }
            }

The variable waterLevel change the texture of the Block, this work so variable change like i want.

But the Item not change to BucketEmpty!

and when leave the game and come back the watellevel is again 0;

i use NBT tags to store the waterLevel, and i know that i need PacketHandler, but what sending from server to client and from client to server. have look in the Tutorials but not help me alot.

Please can someone me explain it!

special how update item in the Hand

Thanks