How long will heroin show on urine test after taking heroin?

Heroin stays in your system for 3-5 days. Drinking a lot of water won't always work so don't rely on it. Water does not "block" the drugs, all it does is flush out your urine. But you need to be drinking lots of fluids especially water but don't drink too much or you can reduce your sodium levels in the blood and slip into a coma. Also if they decide to do hair tests which i doubt they will due to the price of them then you may be in trouble. (Hair tests can see every drug you have done for the past 6 months to 1 year!)