I had 24 hours to take a pre employment drug screen and had smoked the night before. I am a heavy smoker and tried diluting with heavy duty expensive detox liquid from a head shop. I tested myself 3 times at home and failed. So i bought the synthetic urine kit from Puck Technologies (Number 1). It comes with a strap on pouch of liquid urine and tubes to drain the urine thru. The only problem is getting the temp right. The kit comes with a heating pad, but it takes an hour or so to get the urine to 98-100 degrees (There's temp strip adhered to the pouch so you can see the temp rise). So I used a hot water bottle to heat the pouch quickly, went to a convenience store restroom to strap it on and practice, then went to the testing facility. The clip that closes the urine tube can make a slight clicking sound so be careful. They test the temp as soon you hand them your sample. Be sure to let some of the urine go into the toilet after you've filled the cup so it looks like you really peed.

Wasted a ton of money on the dilution stuff. To be sure you'll pass and not blow a wad of moolah, go with the substitution method.