Are drywells a bad idea?
Drywells are a type of drain that collect storm water into the ground. They are not very commonly used anymore. We have seen, however, some contractors still using drywells as their primary method of getting rid of water. Although they would probably disagree with me, I do not believe drywells are a good way of getting rid of unwanted water. We will talk about what a drywell is and also a couple of different reasons that drywells are not a good method for getting rid of water. We will also talk about alternative drainage methods that work better than drywells.
A drywell is basically a hole in the ground filled with stone. Water is fed into the drywell through drainage pipes that collect storm water from various places (sump pump, gutters, yard basins). The water then bleeds into the stone and filters into the ground. It is supposed to work like a leach line does, in that the water will percolate into the ground. The idea behind it is good in theory, but when put into application it doesn’t really work that well.
What normally happens in drywells is that they cannot handle the amount of water fed into it. A drywell acts as a holding place for water. The amount of water that actually absorbs into the ground around the stone is minimal. Let’s say your gutters tied into a drywell. It begins raining and the gutters begin to fill up the drywell. Once the stone is filled as full as it can get with water, it then begins to back water up into the pipe. Eventually it becomes easier for the water to blow out of the bottom of the gutter rather than to push water through the pipe and into the ground. Imagine pouring water into a cup. Once it reaches it full capacity, water begins to spill out over the side of the cup. The same thing happens to your gutters.
Another bad thing about drywells is that if leaves or any other debris gets into the line, the stone becomes clogged easily. Leaves fall into your gutters and then wash down into the drywell. The leaves build up and eventually stop the flow of water through the stone. Now again the water is backing up out of the pipe right next to the foundation of your house.
There are better methods of getting rid of storm water. The best option is to have a residential plumber tie gutters and sump pumps into storm sewer. Many cities, towns, and urban areas have storm sewer available. You may need to pay for a permit to tie in your storm water, but it is well worth the investment. Once you are connected to storm sewer, you can take all the rain and water you want and feed it into the storm sewer. If you are on sewer, and not on a septic system, it may be a good indicator that storm sewer is available.
Many times public storm sewer is not an option, so the second best option is to daylight your water on top of the ground somewhere. Daylight-ing a pipe simply means the pipe protrudes out of the ground somewhere allowing water to flow out of the pipe onto the top of the ground. This can usually be done so that the water sheds into a ditch or off into your back yard somewhere. The water that runs through the pipe and daylights on top of the ground somewhere will never back up (unless the end of the pipe gets covered). Also, debris will flush out the end if it gets into the pipe from the gutter. If you were on a drywell, the debris would clog your stone and pipe. Water that daylights on top of the ground can evaporate and leach into the ground. In a drywell, water would not evaporate but slowly (I mean slowly) leach into the subsoil.
Now you understand why drywells are not a very good way of getting rid of water. There are other simple methods that work much better than drywells, and probably more cost effective too. If you have drywells, consider redirecting the water to storm sewer or simply daylight the water on top of the ground.
Gutter and sump pump tied into storm sewer