The length of time it takes to fill up a french drain depends on many factors. The main ones are:
1) How deep the drain is. If it’s shallow, then the amount of water will not take long to fill up. However, if the drain is deep, then the amount of water will take longer to fill up.
2) The type of pipe used. Some pipes have a larger diameter than others. This means that the bigger the pipe, the more water it can hold.
3) The water pressure at which the water is running into the drain. This means that if two pipes have the same length, the one with a larger diameter will fill up with water faster since more water will be able to flow through it. The higher the pressure, the faster the water level will rise.
4) The size of the water source. If it’s a hose, then it will take longer than if it’s a fire department hose.
4) The size of the inlet. If a pipe has two different inlets, then the one with a larger opening will fill up with water faster. If it’s a small stream, then it will take longer than if it’s a large stream or river. For example, if one pipe has a 1 inch opening and another has a 4 inch opening, then the one with the 4 inch opening will fill up faster since more water can flow through it.
5) The length of time the inlet remains open. If the water source is a hose, then it will take longer to fill up than if it’s a fire department hose or a stream.
Although the above variables mainly deal with length and diameter, there are other factors that will cause the drain to fill up with water faster or slower. These include:
1) The consistency of the material being drained. If it’s sand or large stones, then it will take longer than if it’s mostly mud or clay.
2) The amount of foliage covering the ground. If it’s a forest, then it will take longer than if the ground is bare.
3) The slope of the land. If it’s a hill, then it will take longer than on flat land.
4) The consistency of the pipe material. If it’s PVC, then it will last longer than if it’s clay.
Remember that all these factors work together to determine how long it will take for the drain to fill up with water.
In your case, the pipes are 5 feet deep, made of clay, and the water source is a hose. It might take a day or more for it to fill up.
It is best to evacuate the area as soon as possible, since it may be hours before the water rises high enough to start flooding your house.
Good luck and be safe.
Sources & references used in this article:
- Evaluate the use of reclaimed concrete aggregate in french drain applications. (BH Nam, Z Behring, J Kim, M Chopra – 2014 – rosap.ntl.bts.gov)
- Evaluating the use of recycled concrete aggregate in French drain applications (JP Bassino – Quantitative economic history of Vietnam, 1900)
- Design and construction of a French drain for groundwater diversion in solid waste storage area six at the Oak Ridge National Laboratory (Z Behring – 2013 – stars.library.ucf.edu)
- Flood frequency analysis on the Ardèche river using French documentary sources from the last two centuries (EC Davis, RG Stansfield – 1984 – osti.gov)