How long does it take for opiates to no longer show in a urine screen?

Depends on the drug use (frequency and dosages) and the test. On cheap and inefficient tests, you may be perceived as clear within days, but we have some tests that are looking for any trace residual amounts and it may take months or years for some common drugs to be cleaned out. Some of the new non-tobacco user drug tests that life insurance companies use will raise flags if a person has used tobacco in the past 2-5 years! With the motivation that some companies face (government contracts for instance), some are using some pretty sophisticated tests for common drugs and they may be just about as sensitive. I worked for one company where there were three long-time users and they had little to fear because our "screenings" were cheap and not random. They got by undetected for years (one got sloppy and showed up to work while still high and the other almost terminally OD'ed at home one weekend and it hit the newspapers)--semiannual tests didn't catch them because they were clean by the time the scheduled samples were taken.

Some of the chemicals people use, however, are of types and sophistication that you practically have to be intentionally looking for them, but most opiates have chemical signatures that if a person is using at all, some tests, though definitely not all, will catch you even months later.

Couple days.

Generally not very long - no more than a few days. That's why heroin is so popular in prison. Cannabis hangs around for weeks.

alchohol 3d
weed 3w
opiods/narcotics 1-3mo
could be wrong, shoot for three

12 to 18 hours

some drugs it can take a few weeks to not show.....but remember that if youre doing a drug screen for pre-employment...even though you may have a perscription for say tylenol 3...and you show positive in the test..the employer may consider you to be "masking" for another drug....something illegal....such as heroin....