How long must a perc test hole be pre-soaked before timing the absorption rate?

The correct duration for pre-soaking a perc test hole before timing the absorption rate is at least 4 hours. Pre-soaking is an essential step in conducting a percolation test as it allows the soil to become adequately saturated, which is critical for accurately measuring how well the soil can absorb water. This saturation mimics real-world conditions where soil has been influenced by rainfall or groundwater.

During the pre-soaking period, observing the soil's ability to absorb water is vital, as it helps to avoid misleading results that might occur if the soil were tested too soon after being artificially saturated. If the pre-soak is shorter than 4 hours, the soil might not be fully absorbed or may still be impacted from the initial influx of water, leading to a falsely high absorption rate.

Thus, adhering to the 4-hour pre-soak not only aligns with best practices but ensures that the perc test results are both reliable and representative of the soil's true absorption capabilities. This understanding reinforces the importance of proper testing protocols in the septic installation process, ensuring successful system design and functionality.