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Is Universal Cleaner compatible with septic and greywater systems?Updated 18 hours ago

TL;DR: Universal Cleaner is septic-compatible when used as directed, and it suits greywater systems, aerated wastewater treatment systems (AWTS) and blackwater holding tanks. The two-ingredient formula carries no chlorine bleach, no phosphates, no sodium and no quaternary ammonium disinfectants, so the bacteria your tank relies on aren't disrupted, and the ingredients are readily biodegradable. Built for rural and regional homes, caravans, camper vans, motorhomes, boats and off-grid setups.

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Koh Universal Cleaner box
Koh Universal Cleaner GECA certification

Is Universal Cleaner compatible with septic and greywater systems?

Koh Universal Cleaner is septic-compatible in standard household septic systems when used as directed, and it suits greywater systems, aerated wastewater treatment systems and blackwater holding tanks. The formula has two ingredients, potassium hydroxide and laboratory grade purified water, and leaves out the things most often flagged as a problem for a tank. There is no chlorine bleach, no phosphates, no sodium and no quaternary ammonium disinfectants, and the ingredients are readily biodegradable. Use only as directed, never pour undiluted product into a septic or greywater system, and avoid excessive use beyond normal cleaning applications. Where treated greywater is reused for irrigation, suitability also depends on soil type, on whether you are watering edible crops or ornamentals, and on local council rules.

✓ Septic systems

Compatible with standard household septic tanks and trenches when used as directed. No chlorine bleach and no quaternary ammonium disinfectants, which are the two things most likely to knock over the bacteria your tank relies on to break waste down.

Standard tanks Trench No quat disinfectants

✓ Greywater and AWTS

Suits greywater systems and aerated wastewater treatment systems when used as directed. No phosphates to add to the nutrient load and no sodium, which is what protects soil structure out in the drainage field.

Greywater diversion AWTS No phosphates

✓ Holding tanks

Compatible with blackwater holding tanks in caravans, camper vans, motorhomes and boats when used as directed. Same two ingredients on the road as at home. Clean the surfaces with it rather than dosing the tank.

Caravans Motorhomes Boats Off-grid

What makes Universal Cleaner suitable for septic and greywater?

Koh Universal Cleaner is a two-ingredient formula: potassium hydroxide and laboratory grade purified water. Both dilute during normal cleaning use, and potassium hydroxide neutralises to potassium salts. What keeps it compatible with a tank is mostly what is absent. There are no phosphates, which add to the nutrient load a trench or AWTS has to process and which are linked to algal blooms in waterways. There is no sodium, which affects soil structure where greywater is used for irrigation. There is no chlorine bleach and there are no quaternary ammonium disinfectants, which are the two ingredient classes that reduce the bacteria a septic tank or AWTS depends on. The ingredients are readily biodegradable.

✓ Two ingredients, both simple

Potassium hydroxide and laboratory grade purified water. Both dilute during normal cleaning, and potassium hydroxide neutralises to potassium salts. The ingredients are readily biodegradable.

Potassium hydroxide Purified water Readily biodegradable

✓ What it doesn't contain

No phosphates, so nothing is added to the nutrient load your trench or AWTS has to process. No sodium, which is what protects soil structure in the drainage field. No chlorine bleach and no quaternary ammonium disinfectants, which are the two classes that reduce the bacteria doing the work in your tank.

No chlorine bleach No phosphates No sodium No quat disinfectants

✓ The microbes are doing the work

A septic tank and an AWTS both run on colonies of bacteria that break household waste down into water and gases the ground can take. Cleaners built around chlorine bleach or quaternary ammonium disinfectants reduce those colonies along with the microbes they were aimed at, and once the colony drops off, solids stop breaking down. Universal Cleaner carries neither. It's a cleaner rather than a disinfectant.

No chlorine bleach No quat disinfectants

How should I use Universal Cleaner to stay compatible?

Three rules apply on any septic, AWTS or greywater system. Use Koh Universal Cleaner only as directed, following the dilution and dosage guidance on the label and using it from the trigger bottle rather than straight from the box. Never pour undiluted product into a septic tank, a greywater line or an inspection opening, because concentrated product bypasses the dilution the system is built around. And avoid excessive use beyond normal cleaning applications, since overdosing any cleaner puts an unnecessary load on the bacterial balance your system depends on. Spray, let it work, then wipe, so only dilute residue ever reaches the tank.

✓ Three rules for septic and greywater

1

Use only as directed. Follow the dilution and dosage guidance on the label, and spray it from the trigger bottle rather than straight from the box.

2

Never pour undiluted product into a septic tank, a greywater line or an inspection opening. Concentrated product bypasses the dilution the system is built around.

3

Avoid excessive use beyond normal cleaning applications. More product doesn't clean better, and it loads the system.

Spray, let it work, then wipe. That way only dilute residue ever reaches the tank.

What changes if I irrigate with greywater?

Koh Universal Cleaner suits greywater systems when used as directed, but greywater reuse for irrigation depends on more than the cleaner. Three things change the answer. Soil type matters, because clay and sandy soils handle irrigation water differently. What you are watering matters, because edible crops carry stricter rules than ornamentals. And local council rules matter, because requirements vary by Australian state and council area, with some regions requiring an approved diversion device or treatment system. Check your local guidelines before irrigating with greywater, particularly around edible beds, and treat your AWTS manufacturer's approved-product list as the final word.

⚠ If you irrigate with greywater, three things change the answer

Greywater reuse isn't only about the cleaner. It depends on your soil type, since clay and sandy soils handle irrigation water differently. It depends on what you're watering, because edible crops carry stricter rules than ornamentals. And it depends on your local council, since requirements vary by Australian state and council area and some regions require an approved diversion device or treatment system.

Check your local guidelines before you irrigate, particularly around edible beds, and treat your AWTS manufacturer's approved-product list as the final word.

Soil type Edible vs ornamental Council rules vary
Koh Universal Cleaner

Universal Cleaner

Good Environmental Choice Australia (GECA) certified, Allergy UK certified, Sensitive Choice approved, Eczema Association recognised. Two ingredients, alkaline formulation, no chlorine bleach, no phosphates, no sodium. Septic-compatible when used as directed.

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Koh Bathroom and Shower Cleaner

Bathroom & Shower Cleaner

Foaming spray for soap scum and mineral build-up, and septic-compatible when used as directed. GECA certified, Sensitive Choice approved, Dermatest tested, Eczema Association recognised. Made in Australia.

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Last reviewed: September 2026 · Koh Australia

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