Do French drains need a sump pump?

We get this question a lot from homeowners in Roseville, usually after a wet winter leaves a soggy corner of the yard. The answer depends less on the drain and more on your lot: where the water collects and whether there is anywhere lower to send it. Here is how to tell which situation you are in.

The short answer

Most French drains work without a pump. A French drain is a trench lined with fabric, filled with gravel, with a perforated pipe running along the bottom. Water soaks into the gravel, enters the pipe, and runs downhill to an outlet. That outlet might be a curb drain, a swale, a lower part of the yard, a dry well, or an open pipe end on a slope. As long as the outlet sits lower than the wet area, gravity does all the work and nothing needs power.

A sump pump comes in when there is no lower place to send the water. The pipe empties into a basin buried in the ground, and when the water in the basin rises, a float switches the pump on and lifts the water up and out through a discharge line. So the useful question is not whether French drains need pumps in general. It is whether the water on your property has a downhill path.

What changes the answer on a real property

The first thing is fall. A French drain pipe needs a steady slope along its whole length. If the trench has to be deep to catch groundwater near a foundation, the far end of the pipe can end up lower than the street, the yard, or anything else around it. At that point gravity cannot finish the job.

The second is the shape of the lot. Many Roseville subdivisions are graded fairly flat, with narrow side yards and backyards closed in by fences and block walls. Water that pools in a back corner may have no route to the front without passing under a patio, around a pool, or across a neighbor's yard. Sometimes a careful route along the side yard works. Sometimes it does not, and a pump is the honest answer.

The third is the soil. Clay and hardpan are common around Roseville and the rest of Placer County. Clay holds water and drains slowly, which is often why the yard stays wet in the first place. It also limits the other common gravity option, a dry well, because a dry well only works if the ground around it can absorb water. Where the soil will not take the water and there is no lower outlet, a pump is usually the practical choice.

The fourth is what sits below grade. Many homes here have crawlspaces, and after heavy winter storms some of them collect standing water under the floor. The crawlspace floor is often lower than the yard outside, so a drain under or around it usually has to end in a sump basin.

Finally, there is where the water is allowed to go. You cannot send drainage onto a neighbor's property, and connections to the curb or street can have city rules. It is worth checking with your city before deciding on an outlet.

What you can check yourself

Start by watching the yard during a steady rain or just after one. Note where water stands, where it flows, and how long it takes to disappear. Take photos. Water that is gone in a few hours points to a different problem than water that sits for days.

Next, find the lowest spot you could reasonably send water: the curb, a swale, a lower corner of the lot. Then compare heights. A string line with a line level, stretched from the wet area toward that spot, will tell you roughly whether you have fall to work with. If the wet area sits clearly higher, gravity is likely enough. If it is level or lower, you are probably looking at a pump or a different plan.

Look at your downspouts too. A downspout that empties right next to the foundation is a common cause of a soggy side yard, and fixing it can shrink or remove the problem before you dig anything.

If you already have a French drain, find its outlet and check that it is open and that water comes out after rain. If you already have a sump pump, pour a bucket of water into the basin and confirm the pump switches on and shuts off. Then follow the discharge line and make sure it is not dropping the water back against the house.

When it needs a professional

Call someone when water is getting into the crawlspace or standing against the foundation, because that can affect framing and footings over time. The same goes for an existing French drain that has stopped working. Silt, roots and crushed pipe are the usual causes, and they generally mean digging up and rebuilding part of the line.

A pump that runs constantly, short-cycles, or never seems to run also needs a look. So does any job where the trench would cross gas, water, irrigation or electrical lines. Call 811 before digging so buried utilities get marked. A pump also needs a suitable power source near the basin, which may mean adding a properly protected outdoor outlet.

How this fits with the work we do

When we come out for French Drain Installation, the first thing we do is work out whether gravity can carry the water away. We look at where it collects, measure the fall to possible outlets, and check how the soil behaves. If there is a workable downhill route, we build the drain to use it, because a system with no moving parts has less to go wrong.

If there is no lower outlet, or the drain has to serve a crawlspace, we will tell you that and explain why. In those cases we pair the drain with Sump Pump Installation, set the basin where it can collect from the whole line, and run the discharge somewhere the water will not come back toward the house.

Either way, you will know before any work starts which kind of system your property needs and the reason for it. If you are not sure which situation you are in, request a drainage visit and we will walk the property with you.