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Is Universal Cleaner safe for septic and greywater systems?Updated 6 hours ago

TL;DR: Yes, when used as directed. Universal Cleaner is suitable for standard septic systems, greywater reuse, and holding tanks. The two-ingredient formula (potassium hydroxide and reverse osmosis water) contains no phosphates, no sodium, no chlorine, and no antibacterials. A smart switch for UK rural homes, caravans, camper vans, motorhomes, narrowboats, and boats.


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Koh Universal Cleaner safe for septic and greywater
Koh Universal Cleaner GECA eco-certified (Good Environmental Choice Australia)

Is Universal Cleaner safe for septic and greywater systems?

Yes. Universal Cleaner is suitable for standard septic systems, greywater reuse, and holding tanks when used as directed. The two-ingredient formula contains potassium hydroxide and reverse osmosis water, with no phosphates, no sodium, no chlorine, and no antibacterials. This makes it a smart switch for UK rural homes, caravans, camper vans, motorhomes, narrowboats, and boats. Use only as directed, do not pour undiluted product directly into septic or greywater systems, and avoid excessive use beyond normal cleaning applications. For greywater used in irrigation, suitability also depends on soil type, plant species, and local water authority and council rules.

✓ Septic systems

Compatible with standard household septic tanks. Won't disrupt the bacteria your tank relies on to break down waste.

Standard tanks Bacteria-safe

✓ Greywater reuse

Suitable for greywater systems. For irrigation reuse, suitability also depends on local conditions (see below).

Greywater systems Check local rules

✓ Holding tanks

Compatible with holding tanks in caravans, camper vans, motorhomes, narrowboats, and boats. A smart switch for mobile and off-grid setups.

Caravans Camper vans Narrowboats

What makes Universal Cleaner suitable for septic and greywater?

Universal Cleaner is a two-ingredient formula: potassium hydroxide and reverse osmosis water. Both ingredients dilute and neutralise during normal use. Potassium hydroxide neutralises to potassium salts, and the formula contains no ingredients known to disrupt wastewater systems. There are no phosphates (which can cause algal blooms in waterways), no sodium (which can damage soil structure in greywater irrigation), no chlorine (which kills the beneficial bacteria septic systems rely on), and no antibacterials (which also disrupt septic tank biology). The simple chemistry is what keeps it compatible with septic tanks, greywater systems, and holding tanks. Universal Cleaner is also independently verified by GECA (Good Environmental Choice Australia), Sensitive Choice (National Asthma Council of Australia), Allergy UK, and the Eczema Association of Australasia.

Two ingredients only

Potassium hydroxide and reverse osmosis water. Both dilute and neutralise during normal use. Potassium hydroxide neutralises to potassium salts, and the formula contains no ingredients known to disrupt wastewater systems.

Potassium hydroxide RO water

What it doesn't contain

No phosphates, no sodium, no chlorine, and no antibacterials. These are the ingredients most commonly flagged as risks for septic tanks and greywater reuse.

No phosphates No sodium No chlorine No antibacterials

How should I use Universal Cleaner to stay compatible?

To keep Universal Cleaner compatible with septic and greywater systems, follow three simple rules. First, use only as directed (mix per the dilution guidance on the label and pour into the supplied trigger bottle). Second, do not pour undiluted product directly into septic or greywater systems. The product is designed to be applied to surfaces and rinsed or wiped during normal cleaning, not poured into drains. Third, avoid excessive use beyond normal cleaning applications. Standard household cleaning quantities are well within tolerance, but flushing large volumes of any cleaner into a septic system isn't recommended.

⚠ Compatibility tips

  • Use only as directed (follow the dilution and dosage guidance on the label).
  • Don't pour undiluted product directly into septic or greywater systems.
  • Avoid excessive use beyond normal cleaning applications.
As directed Diluted only Normal cleaning use

Will it work for greywater irrigation?

Yes, in principle. Universal Cleaner is suitable for greywater systems, but greywater reuse for irrigation depends on environmental and regulatory conditions, not just the cleaner. Suitability can vary based on soil type (clay vs sandy soils handle greywater differently), plant species (some plants tolerate greywater better than others, and edible crops have stricter rules), and local water authority rules. UK rules vary by region: England (Environment Agency), Scotland (SEPA), Wales (Natural Resources Wales), and Northern Ireland (NIEA) each set their own standards, and local councils may add planning rules for greywater diversion systems. We recommend checking your local guidelines before using greywater for irrigation, particularly if you're irrigating edible plants or routing greywater into a regulated system.

Greywater reuse depends on local conditions

Universal Cleaner is suitable for greywater systems, but irrigation reuse also depends on factors beyond the cleaner. Suitability can vary by soil type, plant species, and local water authority rules. In the UK, rules vary by region (Environment Agency in England, SEPA in Scotland, Natural Resources Wales, NIEA in Northern Ireland) and local council. We recommend checking your local guidelines before using greywater for irrigation.

Soil type Plant species Local water authority

Koh Universal Cleaner 2L

Universal Cleaner

Two-ingredient formula. Septic-safe, greywater-compatible. A smart switch for UK rural homes, caravans, and boats.

Koh Bathroom and Shower Cleaner 1.8L

Bathroom & Shower Cleaner

Enzyme foam for soap scum and bathroom build-up. Also septic and greywater compatible when used as directed.

Browse all Universal Cleaner products

Last reviewed: May 2026 · Koh UK

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