Coming from one who has had few UPS drug test's due to being a feeder driver. I'm pretty sure you have to fill the container to the top in one shot is so they can check the temperature accurately. The test jars have a temp strip on the side. To hot or to cold and they'll dump it suspecting foul play. I also don't believe you can dilute any drug test by drinking too much water. If drugs are in your system they'll show, maybe low levels but anything showing in a rehab test you're done. Christ when I got hit with a random for feeders 9 times outta 10 I had just taken a leak right before the test guy walked into the office. The poor dude was begging me to drink more water so I'd piss and he could get the hell out of there.