I drank a lot on Saturday night. What are the chances that the EtG test I have to take on Wednesday will detect the alcohol. Does drinking a lot of water between now and then help?

Helps you fail the test.

You have at least 80 hours between your last drink and the test. You will probably pass, but it is dependent on many factors that are unique to you. The range for the test is 60-80 hours. The problems arise if you're a alcoholic or recovering alcoholic, binge drink a lot, or are genetically predisposed to over producing ETG/ETS. That could jog your test results into the Fail Zone.

The scientists who designed this test, who are much smarter then you and me, have built in fail safes. They know that people are going to try to cheat the test because people, not unlike yourself, have a hard time denying themselves something they want. Alcohol. You can't say no and there are many reason why that is. That is left as an exercise for yourself as you quietly contemplate how your life could change if you fail. Moving along, when they test your urine they will test for the ETG/ETS as well as many other chemicals that are usually there in a known range when you're properly hydrated. When you over hydrate these chemicals, along with ETG/ETS, will show up in lesser numbers because you're excreting the water you drank. This is usually a sign of a guilty mind when a subject spoils their sample by over hydrating and is labelled as a fail.

So the best course of action for yourself is to eat and drink normally. Face the music if it comes. If it doesn't maybe take a little time to re-evaluate your life choices.