What is a “big O” agricultural drain?
For many decades the agricultural drain was the one and only material used since it is much faster to install than a clay drain. It is often referred to as Big ”O”. It is flexible and therefore allows to complete the corners of the house continuously. It has holes all around its circumference and can not let rocks in it unless it is broken.
Many contractors still use this material since it is still allowed by the national building code but techniques have evolved a lot since then. The advantage of this drain over the Terra Cota drain is that it has more holes and therefore allows water to penetrate much more easily.
Some agricultural drains are coated with a geotextile to filter the water that penetrates them. The idea seemed good at the time but over time we discovered that this geotextile could lead to clogging of the drain. The geotextile in question would clog with the deposits carried by the soil water and become like a waterproof film around the drain. Unfortunately, when the drain becomes watertight because of this material, there is nothing to do but replace it.
This type of drain has been installed extensively in the last decade. This drain was revolutionary when it first appeared on the market, but the industry soon realized that it had several flaws. It is the enemy of ferrous ochre. Ferrous ochre settles at the bottom of this type of drain and becomes almost impossible to remove. The French drain becomes clogged and water infiltration begins to appear. Roots penetrate this drain very easily and once they have made their way in, it is impossible to remove them since the agricultural drain is flexible and fragile. You can’t use an uprooter because it would tear up the French drain. When we replace a French drain, we do not use this material. Being flexible, it often causes ups and downs around the perimeter of the building causing water retention and sediment deposits.
Why and when to replace an agricultural drain?
The National Building Code of Quebec (NBCQ) specifies that the useful life of this type of drain is 30 years. If it has been properly installed, covered with a good stone bed and is in favorable conditions, it can obviously last more than 30 years. However, it is quite rare to see “Big O” drains with a lot of crushed stone. During new construction, builders tend to neglect the quantity of stones they put on the French drains. This quickly accelerates the degradation of the French drain and makes it easy for residues and roots to penetrate it.
The agricultural drain is flexible and often installed quickly, it is very common to find that there is a lot of up and down in the drain. This is not detrimental to its proper functioning, but it does create favorable conditions for clay or sandy deposits. Residents of the building will not notice a problem until they discover mold or water infiltration in the basement. Unfortunately, once water has infiltrated, the intervention technique will be a bit more invasive. We will have to determine if it is worth the cost to repair the problem or if we will have to replace the entire French drain.
In the presence of iron ochre, the “Big O” drain is the worst to have. Iron ochre is a pasty deposit that clings to the drain dimples. It can become a real nightmare for the building owner. When we are in the presence of ferrous ochre and an agricultural drain, we must almost automatically replace the French drain by a rigid BNQ type drain. Obviously, our experts will be able to determine the seriousness of the situation and determine if periodic cleaning would be sufficient.
When we determine that the agricultural drain has been heavily damaged by the conditions in place and cannot be salvaged, that is when we must replace it. We will install a new foundation waterproofing at the same time. The water infiltration will then be addressed.
Have an agricultural drain inspected or replaced
To inspect an agricultural drain, we can perform a camera inspection through an access hole such as an access chimney or through a pump sump. This type of inspection allows us to see the inside of the drain and determine if it is sagging, if it was installed level, if it is clogged or if it is connected to a drain. However, this type of inspection does not give us a complete picture of the drainage system.
We recommend an exploratory excavation. We proceed with a mini excavation on the edge of the foundation and we will reach the French drain. We will be able to measure the amount of stone on the French drain, if it was installed at the right height, if the water table is higher than the level of the drain, if the stone bed is contaminated by roots or mud and in what condition the foundation is waterproofed. Once this expertise is completed, we will have a complete picture of the drainage system and we will be able to establish a game plan. We will determine if the French drain can be cleaned, repaired or if it needs to be replaced.
If it can be cleaned, we will install cleaning stacks at strategic locations around the house and recommend when the French drain should be cleaned.
If unfortunately the drain cannot be salvaged we will provide a cost estimate to proceed with the work.
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- Call us at (514) 219-0125
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We mainly serve the Montérégie, the Greater Montreal, the South Shore, a part of the North Shore as well as Ontario; and more specifically
Vaudreuil-Dorion – Montreal – Laval – Longueuil – Brossard – Candiac – Salaberry de Valleyfield – North Lancaster – South Glengarry – Alexandria – Hawkesbury – Rigaud – Hudson – Pincourt – Notre-Dame-De-L’ile-Perrot – Lachute – Montebello
We can also travel to more remote areas when it is a complex project and the owner cannot find a certified contractor in their area.