"Hot Water" versus "Low Moisture" Methodology

(referred to in AS/NZS 3733:2018 as “Restorative Cleaning”)

Process…

HWE, commonly referred to as “steam cleaning,” uses hot water mixed with cleaning agents that are injected deep into the carpet fibres to rinse off a pre spray designed to emulsify soils on various types of carpet fibres.
Powerful vacuum from an extractor then extracts the solutions along with dirt and contaminants.

Pros…

Deep Cleaning: HWE penetrates deep into the carpet fibres, making it effective at removing embedded soils, pathogens, allergens, and stains.
Suitable for Heavy Soiling: Excellent for carpets with heavy traffic areas or significant soiling.
Removes Residues: Effectively rinses out strong detergent pre sprays, leaving minimal residue.
Wool Carpets: HWE is often recommended for wool or delicate fibres, provided the pH of the cleaning solution is carefully controlled.

Cons…

Long Drying Time: Carpets can take several hours to dry completely, depending on humidity, airflow, and carpet thickness.
Water Usage: It can use a lot of water, which can be a concern for sustainability or homes with water restrictions.
Potential Overwetting: If not done correctly, it can lead to overwetting, which may cause mould, damage or shrinkage in carpets.

Best For…

Deep cleaning in heavily soiled carpets, homes with pets, high-traffic areas, and where allergens or deep sanitising is needed.

(referred to in AS/NZS 3733:2018 as “Surface or interim Cleaning”)

Process…

VLM uses minimal water, and cleaning agents are typically agitated into the carpet using mechanical equipment like a bonnet or cylindrical brush.
The most common methods include Encapsulation, Bonnet Cleaning, and Dry Compound Cleaning. Encapsulation is the most popular, where dirt is trapped in polymer crystals that are vacuumed up once dried.

Pros…

Fast Drying Time: Since less water is used, carpets typically dry in 1–2 hours, sometimes even faster.
Less Risk of Damage: Minimal moisture means less chance of overwetting, shrinkage, or mould growth.
Eco-Friendly: Uses significantly less water compared to HWE.
Less Expensive: VLM often involves simpler, lighter equipment that is more affordable.
Good for Maintenance Cleaning: Ideal for regular, routine cleaning to keep carpets fresh and reduce dirt build-up.

Cons…

VLM is maintenance cleaning not deep restorative cleaning: VLM doesn’t reach deep into the carpet fibres like HWE, so it may not be effective for heavily soiled carpets.
Residue Build-up: Some VLM methods, especially bonnet cleaning, can leave residues or soil at the base of the carpet if not extracted properly.
More Frequent Cleaning: Since VLM is generally more of a surface-level maintenance method, carpets may need to be cleaned more frequently in high-traffic areas.

Best For…

Light to medium soiling, commercial spaces, routine maintenance cleaning, and situations where fast drying time is essential.

(click images)