Water from outside the home will bring contaminants into the home. If it is flood water from storms, river flooding, hurricanes, etc then it is grossly contaminated and potentially very dangerous. That applies to sewer backup’s also, obviously. “Clean water” losses inside a home, from leaky/broken pipes or hoses poses little risk when it happens. However, if it is not promptly and properly remediated and dried then the water will degrade over time, depending on the temperature – the warmer the faster it degrades. In a few days there were be significant bacteria growth and contamination. Some moulds can begin to grow as soon as 24 hours (again, temperature is a variable) and within a few days there can be hundreds of varieties of moulds flourshing inside you home. Whenever you have any water loss it is recommended you call the Professionals at PuroClean to help you assess the full extent of the damage and to provide professional and professional assistance in remediation, sanitization and drying.