A French drain isn’t one that plays “La Marseillaise” when you hit the flush button. But if you’re struggling with drainage in your yard, a French drain system might very well be the easiest and most beautiful solution.
To look at a French drain you might just think it’s a pretty rock garden path – and that’s one of the best things about it. Better still is that it will solve your garden drainage problems, whether it’s ground and surface water that’s causing all the trouble. Best of all your home and structures foundations will be protected from erosion and flooding – and all with French drains that are easy to install, look good and actually work.
Definition and Purpose
A French drain is a type of drainage system designed to collect and redirect surface water and groundwater away from a specific area, such as a building foundation or a low-lying area of a yard. The primary purpose of a French drain is to prevent water accumulation and damage to structures, landscaping, and surrounding soil. By redirecting water away from the problem area, French drains help to maintain proper drainage, prevent soil erosion, and reduce the risk of water damage.
History and Development
The concept of the French drain dates back to the mid-19th century, when it was popularized by Henry Flagg French, an American lawyer and farmer. French drains were originally trenches filled with rocks or gravel that were used to divert water away from agricultural fields and buildings. Over time, the design of the French drain has evolved to include perforated pipes, which increase the volume of water that can flow through the system. Modern French drains are designed to be more efficient and effective, with a variety of materials and configurations available to suit different applications.
Types of French Drains
There are several types of French drains, each with its own unique characteristics and applications.
Surface French Drains
Surface French drains are shallow trenches that are used to collect surface water and redirect it away from a specific area. They are often used in areas with minor water accumulation issues and are typically installed in a shallow trench, usually 12-18 inches deep. Surface French drains are ideal for collecting water from roofs, sidewalks, and driveways.
Subsurface French Drains
Subsurface French drains are deeper and more effective for managing groundwater. They are commonly used around foundations and basements to prevent water seepage and damage. Subsurface French drains are typically installed in a deeper trench, usually 2-3 feet deep, and are designed to capture and redirect groundwater away from the problem area.
How Does a French Drain Work?
In a nutshell a simple but clever array of perforated pipe in sloping trenches with landscape fabric and decorative gravel or stone on top. Or if you like Henry Flagg French’s old school and innovative 19th century version you can get away with just a rock or gravel filled trench – although it will clog more easily than the modern version.
Benefits of French Drain Systems
French drains have many advantages for homeowners:
- Protect your foundations
- Permanent and low maintenance solution
- Looks good with seamless landscape integration
- Full versatility
- Easy & cheap to install
- Water redirection: French drains redirect excess water away from problem areas, preventing pooling or flooding
- Versatile: Can be installed anywhere, around foundations, in yards or along retaining walls
- Long term solution: With maintenance French drains will last for years
- Improves soil health: Reduces waterlogging, good for plant growth and lawn health
- Customisable: Can be designed to suit your property and style
French Drains vs Other Drainage Solutions
When considering drainage options you need to know how French drains compare to others:
1. Surface Drains:
- Pros: Visible, easy to maintain
- Cons: Ugly, tripping hazards
2. Sump Pumps:
- Pros: Good for basements, can handle lots of water, and can be installed under the basement floor to capture and redirect excess water
- Cons: Needs electricity, regular maintenance and can fail during power outages
3. Dry Wells:
- Pros: Good for areas with permeable soil
- Cons: Limited capacity, can get overwhelmed in heavy rain
4. French Drains:
- Pros: Looks good, good for large areas, passive
- Cons: Installation can be hard work, may need professional help for complex situations
French drains are often the best balance of effectiveness, looks and long term performance for many Australian properties.
How to Install a French Drain in 8 Easy Steps
While most plumbing & drainage work across Sydney and beyond will require the mandatory and skilled workmanship of fully-licensed Sydney plumbers and drainage specialists, installing a French drain is something you can do yourself. Here’s how:
Prepare
The most important thing to know before you start is what’s underneath that garden surface. Because hitting a pipe, electrical line or another underground cable, pipe or installation isn’t just going to mess up your and your neighbour’s place – it can be dangerous.
TIP: Try the Before You Dig Australia service at www.byda.com.au.
Follow the rules
Are you sure there aren’t any zoning or runoff regulations that will ruin your French drain party later on? Another thing to check off the list is whether your proposed drain configuration won’t cause drainage issues for your neighbour, because both of these will get you in hot and expensive water.
Find a slope
It’s a clever drainage innovation but a French drain is still very simple and only works if gravity is on your side. Remember, the whole idea is that water will seep into your laid pipes and be carried away because of the downhill gradient, so:
– Identify the drainage area
– Start at the top
– Route your downhill drainage path
– End the drain where you want the water to go
If your land is flat as a pancake you’ll need to create your own slope by digging shallowest at one end and deeper at the other end with at least a 1-2% grade.
Dig the trench
You’ll need it about 30cm wide and 50cm deep and make sure you don’t disturb the natural slope of the land with a poorly dug trench.
Line it
Your French drain will be lined with fabric – but it needs to be fully water-permeable. We recommend genuine landscape fabric which is designed for this purpose and is installed by:
– Rolling it out over the trench
– Leaving a 30cm gap on both sides
– Tamping down to fill the gaps
– Securing it in place
Add the gravel
Now pour a 5-10cm layer of gravel on top of the fabric.
Add the pipe
Any drain pipe will do but PVC will last the longest and work the best. It will need to have holes or perforations to do the drainage work and those holes should be laid face down and then the whole thing covered with another thin layer of gravel to within 5-10cm of the top of the trench.
Done
Fold the remaining fabric over the gravel and cover it all in soil. You can then finish off the look however you like – grass or just decorative stones.
French Drain Essentials
Get these before you start:
- Perforated pipe (PVC or corrugated)
- Landscape fabric
- Gravel or crushed stone
- Sand (for bedding)
- Topsoil (for finishing)
- Digging tools (shovel, pickaxe etc.)
- Level or laser level
- Tape measure
- Safety equipment (gloves, safety glasses)
Professional or DIY French Drain Installation
Deciding between professional installation and DIY depends on:
Professional Installation:
– Pros: Expertise in design and local regulations, proper equipment, warranty on work
– Cons: Higher upfront cost
DIY Installation:
– Pros: Cost savings, personal satisfaction
– Cons: Risk of errors, time consuming, may not have proper tools
Consider professional installation for complex projects, areas with utilities or if you’re not sure of local regulations. DIY is suitable for simple, straightforward installations in open areas.
French Drain Costs
Costs will vary depending on:
- Length of drain
- Depth of installation
- Soil type and excavation difficulty
- Materials used (e.g. type of pipe, gravel quality)
- Professional or DIY
In Australia professional installation can cost between $100 to $250 per linear metre. DIY will save you money but will take time and effort.
Regulations and Permits for French Drain
- Council Approval: Check if you need approval from your local council.
- Stormwater: Make sure your drain complies with local stormwater regulations, including proper connection to a storm drain.
- Property Boundaries: Check your drain doesn’t impact neighboring properties.
- Environmental: Some areas may have restrictions due to environmental concerns.
- Utilities: Always check for underground utilities before you dig.
Contact your local council or a licensed plumber for more information in your area.
French Drain Maintenance
Maintenance will keep your French drain working for years to come:
- Check-up: Inspect for clogging or damage at least twice a year.
- Debris removal: Clear leaves, twigs etc. from the surface of the drain.
- Flushing: Flush the system with water every now and then to clear sediment.
- Landscape maintenance: Trim nearby plants to prevent roots from entering the drain.
- Grate cleaning: If your drain has a grate, clean it regularly to allow water to flow.
- Professional check-up: Consider having a professional check the system every few years.
French Drain Problems
Even well installed French drains can have issues. Here are common problems and fixes:
- Clogging: If water isn’t draining, the pipe may be clogged. Flush the system or use a plumber’s snake to clear blockages.
- Surface water pooling: This could mean the drain is overwhelmed or not sloped correctly. Add more drainage or adjust the slope.
- Erosion around the drain: Add more gravel or adjust landscaping to prevent soil erosion.
- Foul odours: This means standing water or organic matter buildup. Flush the system and check the slope.
- Frost heave: In cold climates make sure the drain is installed below the frost line to prevent damage from freezing.
Advanced French Drain Installation
For more complex drainage issues try:
- Dual pipe systems: A second pipe for extra drainage in heavy rainfall areas.
- Sump pump integration: A French drain with a sump pump for basements or areas below the water table.
- Geotextile wrapping: Wrap the entire drain in geotextile fabric for extra filtration.
- Cleanout ports: Install access points for maintenance and cleaning.
- Bioswale integration: French drains with bioswales for natural filtration.
Need help with your French drain?
Every time it rains and pours across Sydney we are all reminded about the importance of good, professional stormwater drainage solutions that protect your home, family, garden, investments – and sanity!
Blacktown, Engadine, Castle Hill, Casula and Penrith are some of the most flood prone areas according to NRMA but nowhere is immune. If you want to put your French drains in the best possible hands give Sydney’s friendliest drainage experts here at Rapid Service Plumbing a call.
