Clean, grey and black water: the categories of water damage

Why the category matters

Two floods that look the same can call for completely different responses. A burst supply pipe over a carpet may mean drying and keeping almost everything. A sewer backup over the same carpet means removing it, along with the drywall it touched.

The restoration industry’s standard for water damage, the ANSI/IICRC S500, sets out three categories based on how contaminated the water is. Insurers and contractors across Canada use the same terms.

Category 1: clean water

Water from a sanitary source that poses no substantial risk from skin contact or swallowing.

Typical sources

• A burst or leaking supply pipe
• A failed supply hose to a tap, toilet, washing machine or fridge
• An overflowing sink or bath, with no contaminants
• A leaking water heater
• Melting snow or rain coming directly through a roof, before it has run through much of the building

How it is handled

• Extract and dry in place where possible
• Carpet can usually be saved, with the underpad replaced
• Drywall that is firm can often be dried
• The emphasis is on speed

Category 2: grey water

Water with significant contamination that could cause discomfort or illness on contact or if swallowed. It may contain micro-organisms, or the nutrients they feed on, and chemical or physical contamination.

Typical sources

• Discharge from a washing machine or dishwasher
• An overflowing toilet bowl with urine but no faeces
• A leaking aquarium or waterbed
• Sump pump failure, depending on what is in the pit
• Water that has come through a ceiling and picked up building dust and debris

How it is handled

• Carpet underpad is removed. The carpet itself may be cleaned and kept if dealt with quickly.
• Affected surfaces are cleaned as well as dried
• More protective equipment is used
• Porous materials that were heavily wetted are assessed case by case

Category 3: black water

Grossly contaminated water that can contain harmful agents and cause serious illness.

Typical sources

• Sewage, and any backup from beyond the trap of a fixture
• A toilet overflow containing faeces
• Flood water from rivers, streams and lakes
• Surface water entering from outdoors, which carries soil, fertiliser, animal waste and fuel
• Wind-driven rain from severe storms, in some circumstances
• Any water that has stood long enough to support heavy microbial growth

How it is handled

• People not involved in the work, particularly children, older people and anyone with a weakened immune system, are kept out
• Workers wear full protective equipment
• Porous materials that were touched are removed and discarded: carpet and underpad, drywall, insulation, particleboard, mattresses and upholstered furniture
• Remaining structure is cleaned, then disinfected, then dried
• Contents are sorted. Hard, non-porous items can be cleaned and disinfected. Most porous items cannot.

Clean water does not stay clean

The category describes the water at a point in time, not just at its source. It can get worse in two ways.

Time. Clean water left standing warms up and bacteria multiply. After a couple of days, a Category 1 loss is commonly treated as Category 2, and beyond that as Category 3. This is one reason quick action saves materials and money.

What it touches. Clean water that runs through a dirty crawl space, over soil, through a ceiling full of old insulation and rodent droppings, or across a floor with pet waste picks up contamination on the way.

A restorer therefore asks not only where the water came from but how long it sat and what it passed through.

The other label: class

You may also see a class on a drying report. Where category describes contamination, class describes how much water has to be evaporated: from a small amount in part of a room with little absorbed, up to a space where water has soaked into low-porosity materials such as hardwood, plaster and concrete that need special drying methods. Class determines how much equipment is needed and for how long.

What you can do safely

Category 1, small and fresh: a householder can extract and dry it, taking care with electricity.

Category 2: wear gloves and waterproof boots, keep children and pets away, remove the underpad, wash and disinfect hard surfaces, and dry quickly. Get help if it is more than a small area or has sat.

Category 3: limit your involvement to stopping the source where that is safe, protecting yourself and calling for help. If you must enter, wear waterproof boots, gloves, eye protection and a suitable respirator, do not use a household vacuum, and wash thoroughly afterwards. Do not run the furnace fan.

Common questions about particular cases

Rain through the roof? Direct rain is close to clean, but it becomes contaminated as it passes through roofing, insulation and ceiling materials. It is often treated as Category 2.

Sump pump overflow? Ground water from the weeping tile is not sewage, but the pit is not clean. Usually Category 2, and Category 3 if the sump is connected to a system that backed up.

Toilet tank or supply line? Clean. The bowl is not.

Basement flood from a storm? If water came in over the ground or up through the drains, Category 3.

Hot water heating system leak? The water may contain treatment chemicals and rust. Often Category 2.

Insurance and the category

The category affects the scope of the claim, because it decides what must be replaced. It is separate from the question of coverage, which depends on the source: a burst pipe, sewer backup and overland water fall under different parts of a policy or different endorsements. A contractor’s report should state the category and the reason for it.

More: water damage restoration and sewage backup cleanup.