How deep can you go with a French drain?

French drain depth: About 8 inches to 2 feet deep should be sufficient for many water-diverting projects, though related systems, such as those built around foundations and sub-ground living spaces, as well as the bases of retaining walls, may be deeper.

How shallow can a French drain be?


Because there is a direct relationship between the diameter of a drain pipe and its relative effectiveness, make your trench no smaller than 12 inches wide, and aim for a depth between 18 and 24 inches.

What’s better French drain or trench drain?

French drains have toughness in common with trench drains since the French type must handle groundwater that’s subject to hydrostatic pressure (the pressure water exerts due to the force of gravity). French drains are very effective at redirecting water away from structures and preventing damage to the foundation.

How deep should a French drain be UK?

The trench should be about 300-500mm deep, and dug so that it slopes at a ratio of 1:50. That means that for every 2 meters of trench length, it should fall 40mm. Digging your trench – You can do this using manual labour, or you could hire a mini digger to make the job much easier.

How far should French drain be from foundation?

Recommended French Drain Installation Distance

We recommend installing the french drains between 2 and 5 feet away from the foundation. There are a few variables that impact the exact distance to dig the new drain lines to carry water away from your home.

What is the minimum depth for drainage pipe?

Pipes laid at depths less than 600mm and which are not under a road should, where necessary, be protected against damage by placing over them a layer of concrete, paving slabs or similar. A minimum 75mm cushioning layer of granular material must be laid between pipes and the slabs or concrete.

How do you drain subsurface water?

If surface drainage is not satisfactory for removing excess water and salts, subsurface drainage is done. This employs the use of open ditches, buried or perforated tiles, or pumped drainage wells. Open ditches are useful for removing large amounts of water when the water table is too high, or the slope is too slight.

Should French drain be below frost line?

A properly installed French drain will begin at the depth of the base of the perimeter beam and is installed with a 1% minimum slope (1 inch in 8 feet). This is usually below the frost line. Generally, those placed below the frost line tend to provide year-round performance, especially in cold regions.

What size gravel is best for French drain?

1/2 inch to 1 inch across

Gravel used for this layer is typically 1/2 inch to 1 inch across — the larger it is, the better the water flow and less chance of clogs and blockages. For a French drain without a perforated pipe, opt for even larger gravel, such as 1 1/2 inches across.

How deep should a drainage trench be?

A drainage trench should be at least 18 inches deep. This allows you to install a gravel bed, as well as an adequately-sized pipe to carry away water. It also allows you to cover the pipe to protect it and make your drainage trench an attractive lawn feature.

Why do French drains fail?

Over time, a French drain may become clogged. Tiny soil and clay granules slip through the pores of the landscape fabric and gradually build up inside the pipe. Another common cause of French drain clogs is root intrusion from grass, shrubs, and trees.

How many years does a French drain last?

approximately 30 to 40 years

Generally speaking, a French drain will last approximately 30 to 40 years.

How much slope does a French drain need?

1 percent

French drains need to have a slope of at least 1 percent, so the force of gravity will work for you. This means that the drain should slope down a total of at least one inch for every 10 feet of pipe.

How do you build a French drain that lasts forever?

Quote from the video:
Quote from Youtube video: We just cut the sod off and the pipe was pushed up to the surface. The frost will do that in Michigan and any place in the north where you have a real winner.

Are French drains worth it?

French drains are very efficient at relocating water from heavy rain, but only on properties that are adequately drained. That means if you live near a body of water, have shallow groundwater, or your area is designated as a flood zone, a French drain might do nothing for you.

Should French drain be next to foundation?

It can be placed inside a basement or outside along the foundation. If water pressure beneath the slab forces water into the basement via the joins of wall and floor or through cracks in the foundation, then a French Drain will be placed inside the basement along the wall and floor joins.

Do you cap the end of a French drain?

Cap the end at beginning of the system. Level rock 4 inches from the top of the trench. Note: If you just dump rock on top of the pipe, it will shift to one side of the trench. Make sure to keep it in the middle of the trench.

How much does labor cost to install a French drain?

Expect to pay between $10 to $50 per linear foot to install an exterior French drain. Interior French drains are often costlier due to the need to break out concrete in a basement floor to excavate beneath and install the drain, so this type of drain runs an average of $40 to $100 per linear foot.

How much gravel do I need for a 50 foot French drain?

To calculate gravel needed for a 50′ french drain, multiply the length of the trench by the width and depth. If you plan to lay down 4 inches of gravel, multiply 50 feet x 4 inches = 200 cubic feet.

How long does it take to install French drain?

Completed Installation Time

6 – 8 Hours | A simple french drain installation can be done in one day by a team of professional landscapers barring any complications. 1 – 2 Days | If you rent a trencher and do the project yourself, you can expect it to take up most of your weekend.