Stop Yard Flooding in Its Tracks with a French Drain

French drains have become a popular solution for managing water on properties, whether for yard drainage or flood response. In this write-up, we will explore the benefits and limitations of 

French drains, provide step-by-step instructions for installation, and address frequently asked questions about French drains. Additionally, we will discuss French drains in New Zealand and the importance of preventing flood damage to the community.

Advantages and Disadvantages of French Drains

  • French drains offer several advantages, including adequate drainage and prevention of water damage to properties. They work by directing water away from the foundation and into a drainage system. 
  • However, French drains have limitations, such as maintenance requirements and the potential for clogging. Regular maintenance is necessary to prevent the buildup of debris, which can cause clogs and reduce the system’s efficiency. 

Additionally, installing French drains requires proper slope and grade to ensure adequate drainage, and selecting suitable fabric is essential to ensure longevity and efficient operation.

Best Fabric and Stones for French Drains

French drains effectively manage excess water on properties, but selecting suitable materials is crucial to ensure proper function. Here are some tips based on the provided web search results:


  • Use a non-woven geotextile fabric weighing at least 4 ounces per square yard to provide excellent filtration while allowing water to pass through.
  •  Install the fabric on the sides and bottom of the trench and extend it at least 6 inches above the top of the stone or gravel layer to prevent soil from entering the drainage system.


  • Use a coarse, angular stone or gravel with particle sizes ranging from 3/4 to 2 1/2 inches to allow for proper drainage and prevent clogging.
  •  Avoid rounded stones or smooth river rock, as they can shift and create voids in the drainage system over time.

Best Fabric for French Drains:

  • Non-woven geotextile fabric provides excellent filtration while allowing water to pass through and can be used to line the trench or the pipe to prevent clogging.

Best Stones for French Drains:

  • Base gravel #3 is recommended as it is suitable for French drains, whether using a perforated pipe or not. 
  •  Large stones are ideal for bottom layers and should be no smaller than an inch.
  •  Other options for landscaping stones include beach pebbles, river rocks, and gravel pits, which can be used for decorative purposes or as a straightforward fix for pooling water.

French drain fabric and stones must match drainage needs, soil type, and climate. French drains should use non-woven geotextile fabric and coarse, angular stone or gravel with particle sizes from 3/4 to 2 1/2 inches.

Installing French Drains

To install a French drain, start by trenching in the direction you want the water to go, with a slope of 1 inch for every 8 feet in length. Next, add a layer of washed drainage gravel that will lace the newly-installed pipe’s upper and lower parts. 

Choose a high-quality, non-woven fabric that is resistant to clogging and deterioration. After adding the material, lay the pipe and slope it downwards to ensure water flows away from home. The last step is to refill the trench with topsoil to grade.

Tools and supplies 

ShovelFor digging the trench
Tape measureFor measuring the trench
LevelTo ensure the trench is level
Perforated drainage pipeTo allow water to flow through the drain
Rubber malletA rubber mallet can be handy for tapping fittings and connections into place without damaging them.
Landscape fabricTo prevent soil and debris from clogging the drain
GravelTo surround and cover the drainage pipe
Sump pump (optional)To pump water out of the drain

To add to the list of tools that might be handy when doing French drains, a wheelbarrow or a tarp can help move and dispose of excess soil. A drain snake or a plumbing auger can also help clear clogs. 

Regarding purchasing tools in New Zealand, several options are available, including hardware stores, home improvement centres, and online retailers. Some popular places to purchase tools in New Zealand include Bunnings Warehouse, Mitre 10, and Trade Depot.

Best Types of Drainage Pipe:

  • PVC: This is the most commonly used material for French drain pipes due to its durability, affordability, and ease of installation.
  •  Corrugated plasticThis is a more flexible option that can be easier to work with and is more resistant to crushing or bending.

Are French drains a good idea? 

French drains are a reliable and cost-effective solution for managing water on properties, whether for flood response or yard drainage. 

They use a perforated pipe surrounded by gravel or rock to intercept excess water and redirect it away from the property’s foundation. This helps prevent flooding and reduces the risk of long-term water damage.

French drains can last 30-40 years and are aesthetically pleasing with decorative coverings. They also reduce musty smells in moist crawl spaces and other property sections, preventing mould and mildew growth. A French drain reduces soil saturation by diverting excess water from the property and foundation, improving indoor air quality.

In addition to preventing musty smells, French drains are highly effective for managing water in vast lawns and backyards, reducing the risk of flooding, erosion, and other types of damage. French drains are a versatile solution for managing water on properties, offering long-lasting and practical benefits.

How Deep Should a French Drain Be?

French drains are trenches that remove excess water from an area and prevent water damage. The depth of a French drain depends on the type of material used and the property’s specific requirements.

Recommended Depth

  • Depending on the source, there are different recommendations for the depth of a French drain.
  •  Some sources suggest a depth of around 8 inches to 2 feet, while others recommend a depth of 1.5 feet or deeper.
  •  A general guideline is that the trench should be at least 12 inches deep and slope gently downhill.
  •  Consulting with a professional can determine the correct depth based on the type of material used, the slope angle required for the pipe, and the property’s specific requirements.

Correct Installation

  • To install a French drain correctly, the trench should be at least 12 inches deep and 2 feet in width.
  •  The bottom of the trench ideally needs to slope gently downhill and away from the house to prevent water damage.
  •  French drains are commonly made of landscape fabric, gravel, and perforated pipe.
  •  Smoother but perforated, 8-12 inch PVC or corrugated pipe is recommended as it prevents standing water and adds stability.
  •  Steel or plastic pipes are not recommended as they might corrode, rust, or break easily.

By following these guidelines, property owners can benefit from a reliable and long-lasting solution for managing excess water and preventing water damage. 

Consult a professional to ensure the French drain is installed correctly and effectively.

Can I do a French drain myself? 

French drain installation can be a DIY project, but it is crucial to consider the complexity of the installation process, physical demands, and compliance with building codes and regulations. I.e., Selecting suitable fabric and ensuring proper slope and grade. 

If you have the necessary knowledge, techniques, and tools, as well as the physical strength and endurance, you can complete the installation and save on labour costs. 

However, you may need clarification on any aspect of the installation process. 

What is the difference between a French drain and a trench drain? 

French drains and trench drains are two different types of drainage systems. Here are the key differences:

French Drain

An underground drainage system comprises a trench filled with permeable materials, such as gravel or river rock, and a perforated pipe at the bottom. Used to collect and redirect groundwater or runoff water, keeping it away from the foundation of buildings and other structures such as rain gardens. Often used in yards or gardens to improve drainage.

Trench Drain

Surface-level drainage system

It consists of long, narrow channels or troughs with a grate on top designed to collect and redirect surface water from a specific area, such as a driveway or patio requires a slope to be adequate so that the water can flow toward the collection area often used in outdoor hardscaping projects or in commercial applications, where surface water management is crucial.

French drains in New Zealand: How to verify zoning and get permits

In New Zealand, French drains have become a popular solution for managing water on properties. To ensure compliance with local zoning and regulations, verifying and obtaining the necessary permits before installation is essential. Failure to do so may result in legal or financial penalties.

In New Zealand, the Building Code sets the minimum standards for building work, and local councils enforce compliance. It is essential to ensure that the French drain installation complies with these standards.

To ensure compliance, homeowners can consult a licensed building practitioner, or CPEng, who can verify any relevant design assumptions. Checking plumbing and gasfitting standards may also be necessary.

It is also important to contact local utilities to have underground utility lines marked before any digging begins. Checking local building codes and obtaining the necessary permits before installing a French drain can help avoid potential legal issues and ensure that the project is completed to a high standard.

Additionally, homeowners can check French drain costs in New Zealand, as these costs can vary widely based on the location and length of the drain.

Know Your Zoning Laws 

Firstly, in New Zealand, the zoning of a property can affect the installation of French drains. A considerable lot residential zone, defined in standard 8 (zone framework standard) of the national planning standards or an equivalent zone, may have different requirements for drainage systems than other zones.

In terms of the installation of sanitary plumbing and drainage systems, it is required to be by the New Zealand Building Code clause G13 Foul water or AS/NZS 3500 Plumbing and drainage. The objectives of Clause G13 are to safeguard people from illness due to infection or contamination as a result of personal hygiene activities.

Additionally, zoning is essential for funding local government services such as sewerage, rubbish collection, and water provision.

However, the search yielded no specific information regarding the zoning of French drains in New Zealand. It is recommended to consult with a licensed plumber or relevant local authorities for more details on zoning regulations for drainage systems in New Zealand.

In conclusion, while New Zealand’s zoning regulations can impact drainage system installation and maintenance, further research and consultation with professionals are needed to understand the specific zoning requirements for French drains.

Minimizing Flood Damage: Plumbing Tips

Key Points:

  • French drains can prevent water damage in residential and commercial properties.
  •  A perforated pipe covered with gravel should be installed at the bottom of the trench.
  •  The trench should slope slightly in the direction where the water needs to be diverted.
  •  Proper guidelines should be followed when installing a French drain
  •  Annual maintenance is necessary, and electric drain snakes can help clear stubborn clogs
  •  A cost estimate from a reputable plumber is crucial to avoid overcharging and ensure a smooth installation process.

Uncovering the Secrets of French Drainage Depths & Widths

Say goodbye to a soggy yard after every rain with the help of the French Drain Man! Watch Rob with over 30 years of experience in solving yard water drainage problems, these Michigan-based experts are masters in constructing contained French and curtain drain systems that fix your problems for good. To find out how deep and wide you should dig the trench in your yard, check out the video embedded in our blog post. Don’t forget to subscribe if you find it interesting!

FRENCH DRAIN MAN. (2020, March 2). How Deep & Wide Should a French Drain Be? [Video]. YouTube.


In short, French drains are the MVPs of yard drainage and flood response. They may have limitations, like the occasional clog, but they make up for it with the ability to prevent water damage and flooding. 

Selecting suitable materials, following proper installation procedures, and obtaining necessary permits can ensure that these drains do their job effectively. 

So don’t let water bog you down – consider French drains to keep your property high and dry! And thank you for reading!

Leave a comment