House problems · Iron ochre · French drain
An orange deposit in the sump is iron ochre, and on the South Shore it is not rare. Here is how it clogs the drain, how it is maintained, when it is replaced and what it changes at the sale.
Iron ochre is a gelatinous rust-coloured deposit produced by bacteria that oxidize the iron dissolved in groundwater. In the clay, iron-rich soils of Montreal's South Shore (Brossard, Longueuil, Saint-Hubert, Saint-Lambert, La Prairie) and several Laval sectors, it clogs the French drain in five to ten years in active cases, twenty to thirty elsewhere, and ends up pushing water up at the joint between the basement floor and walls. The signs: orange deposits in the sump, the pump or the floor drain, a sulphur smell, recurring dampness along the slab edge. Pressure cleaning of the drain by a specialist, every three to five years in at-risk sectors, keeps an accessible drain working; when it is irreversibly clogged, it is replaced by a drain compliant with the BNQ standard for ochre soils, with clean-out chimneys, which costs $12,000 to $30,000 on the 2026 market. A seller who knows about the problem must disclose it; the buyer of a house in the clay sectors asks for a camera inspection of the drain.
Groundwater in clay soils contains dissolved iron; naturally present iron bacteria oxidize it and produce a rust-coloured gelatinous sludge, iron ochre, that settles in the slots and inside the French drain, in the surrounding gravel and up into the pump. The phenomenon is chemical and biological, not a construction defect: a new, perfectly laid drain clogs anyway if the soil is ochreous. Its speed depends on iron content, oxygen and the water table: five to ten years in active cases, twenty to thirty in slow ones.
The clay plains of the Champlain Sea: a large part of the South Shore (Brossard, Longueuil, Saint-Hubert, Saint-Lambert, La Prairie, Candiac, Sainte-Julie, Boucherville depending on the street), Laval sectors (Sainte-Dorothée, Fabreville, Chomedey), the North Shore (Terrebonne, Mascouche, Repentigny) and the eastern crown of Montreal. Within one city, one street is affected and the next is not: recent sales on the street, and the neighbours, are the source. Our neighbourhood guides for Brossard and Longueuil mention it when inspectors flag it.
Orange or rust deposit in the sump, on the pump and in the pipes; water rising at the basement perimeter after rain or thaw; rotten-egg smell (sulphide) near the pump; efflorescence and dampness at the base of foundation walls; a pump running more than before. A camera inspection of the drain, through the sump access or a clean-out, shows the clogging and its extent.
| Intervention | When | 2026 market cost |
|---|---|---|
| Camera inspection of the drain | Before buying, or at the first symptoms | $300 to $600 |
| Pressure cleaning of the drain (ochre specialist) | Every 3 to 5 years in at-risk sectors, if the drain has access points | A few hundred to $1,500 depending on access |
| Adding clean-out chimneys to an existing drain | When the drain still works but has no access | Variable, a few thousand dollars |
| Replacement with a BNQ-compliant drain for ochre soils (rigid pipe, membrane, chimneys, sealed sump) | Irreversibly clogged drain | $12,000 to $30,000 depending on length, depth and access |
The BNQ drain does not make ochre disappear: it allows cleaning without excavating, turning an irreversible problem into periodic maintenance. Keep the cleaning invoices: they prove the house is looked after.
A seller who has diagnosed ochre, had the drain cleaned or replaced, or suffered infiltration must disclose it (article 1726 of the Civil Code and the Declarations by the seller). A clean file (BNQ drain, dated cleanings, recent camera) sells without a discount on the South Shore, where buyers and their inspectors know the phenomenon; an original 1970s drain never inspected on a street known for ochre earns a camera-inspection condition and, depending on the result, a credit or a replacement before the sale. See the French drain at end of life.
No, it is a sludge of iron and harmless bacteria; the risk is to the drain, the basement and the wallet.
No, it comes from the soil. You manage it: accessible drain, periodic cleaning, sealed sump and maintained pump.
Clogging that causes infiltration not apparent and unknown to the buyer can be; case law weighs what a prudent buyer would have seen (deposits in the sump) and what the seller knew.
No: much of the South Shore is one. Buy with an inspected drain, a maintenance plan and a price that accounts for it.
These problems are easier to settle before listing than after the buyer's inspection: see the pre-purchase inspection in Quebec, latent defects in Quebec and renovating before selling.
The Loaa & Manseur team, led by Lotfi Manseur and Loaa Al Daow, is the number 1 team at RE/MAX Platine in 2024 and 2025, 6th RE/MAX team in Quebec, 15th in Canada and in the global top 50 of large residential teams according to the official RE/MAX ranking, computed on actual transactions. Its Google profile counts 221 reviews with a 4.9 rating. Its offices are at 55 avenue de l'Équinoxe in Brossard, one bridge from the island, and every broker's licence can be checked in the OACIQ public register. Three things to verify yourself before calling us, and to demand of any other broker.
Also available in French: version française de ce guide.
Published September 7, 2026 by the Loaa & Manseur team, the number 1 team at RE/MAX Platine in 2024 and 2025, 6th RE/MAX team in Quebec, 15th in Canada and in the global top 50 according to the official RE/MAX ranking. Tell us about your project.
Équipe no 1 de RE/MAX Platine en 2024 et en 2025, 6e au Québec, 15e au Canada et dans le top 50 mondial au classement officiel RE/MAX. Réponse en moins de 24 heures, sept jours sur sept.