What is iron ochre?

Iron ochre is a red or orange deposit sometimes found in drainpipes. Its presence and scope are due to iron-eating bacteria found in soil and underground water. To prevent the negative consequences of iron-eating bacteria, you need get an iron ochre test. AmeriSpec now does your iron ochre testing.

How does iron ochre develop?

Iron Ochre is more likely to develop in a more aerated soil, such as the sandy soils containing silt.

Chemical reaction: When the soil contains iron, it migrates along with the water towards the drainage system. When it comes in contact with the atmosphere, it forms a sludge of iron hydroxide.

Biological process: When iron bacterium is present within the water table, this bacterium, following oxidation of the iron upon coming into contact with the atmosphere, produces a gel-like mass. When the biological process adds up to the chemical reaction, the oxidation effect is increases. In both cases the result is the formation of a viscous deposit on the corrugated wall of drain pipes. This deposit is what we call iron ochre.

A chemical or biological occurrence is faster when:

  • the soil tends to be neutral (pH of approximately 7)
  • the wall of the drain is corrugated;
  • the openings of the drain are punched instead of cut out, creating attachment zones for the deposits
  • the drain is wrapped in a filtering membrane.

Under the action of iron ochre, even crushed gravel loses its filtering properties. The soils rich in iron and in iron bacteria will produce ferrous deposits indefinitely.

What happens when iron ochre is present?

  • The presence of iron ochre causes sludge deposits to accumulate in the rain water catch basin and in ditches.
  • Iron ochre creates reddish deposits on the concrete slab of basements. These deposits give a sulfur-like odour.
  • Iron ochre obstructs agricultural tile drains. As runoff water is no longer channeled at a distance from the foundations, iron ochre infiltrates the basement, at the junction between foundation walls and slab.
  • The presence of iron ochre obstructs the backflow valves.

Information provided by the Régie du Bâtiment du Québec web sit