Are Dishwashing Tablets septic compatible?Updated 14 hours ago
TL;DR: Dishwashing Tabs are septic-compatible when used as directed, and they suit grey water systems, aerated wastewater treatment systems, worm-farm systems, vans, caravans and boats with an on-board dishwasher. There are no phosphates and no chlorine bleach in the formula, so the bacteria your system relies on to break down waste are not disrupted. Cleaning is done by oxygen-based bleaching and a two-enzyme blend instead.
Are Dishwashing Tablets septic compatible?
✓ Septic-compatible when used as directed
Two things do the work here. There are no phosphates and no chlorine bleach, which are the two ingredients that upset the bacterial balance in a septic tank. And the cleaning is done by oxygen-based bleaching, which breaks down into water and oxygen, alongside a two-enzyme blend of protease and amylase.
That covers standard household septic tanks, aerated wastewater treatment systems and older tank-and-trench setups. Koh does not make antimicrobial claims for Dishwashing Tabs and they are not tested or registered as a disinfectant.
How should I use them on a septic system?
✓ Three rules for septic and grey water
Use only as directed. One whole tab per wash, in the dispenser or flat on the tub floor for quick cycles. Don't cut a tab in half and don't add a second one.
Never pour undiluted product into a septic tank, a grey water line or an inspection opening. That includes unwrapping a tab and tipping the contents down a drain.
Avoid excessive use beyond normal cleaning. More detergent doesn't clean better, and it loads the system for no gain.
Around 2 months in an average home at one tab per wash.
What about grey water systems?
✓ Suitable for grey water diversion
Wastewater from Dishwashing Tabs carries no phosphates and no chlorine bleach from the formula, which is what matters for a diversion line or an aerated system running on aerobic bacteria.
⚠ If you irrigate with grey water, three things change the answer
Suitability for reuse isn't only about the detergent. 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 state and council area. Check your local guidelines, and treat your system manufacturer's approved-product list as the final word.
What about off-grid properties, vans and boats?
✓ Works for
Rural and regional homes on tank or bore water, off-grid builds with composting or worm-farm systems, camper vans and caravans with portable grey water tanks, and boats with an on-board dishwasher. Dishwashing Tabs travel well too. Wrapped tabs in a cardboard box, no liquid to leak and no powder to spill.
Store the box sealed, dry and out of direct sun. The PVA film starts dissolving as soon as it meets moisture, so a damp cupboard in a van is worth avoiding.
Why does the formula make a difference on septic?
✓ What Koh puts in instead
Rather than chlorine bleach, the formula uses sodium percarbonate, which releases oxygen in the wash and breaks down into water and oxygen. Rather than phosphate builders, it uses sodium citrate and sodium silicate to deal with hard water. Protease and amylase handle protein and starch.
Ten ingredients in total. GECA certified and Sensitive Choice approved.
Around 2 months in an average home. 10 ingredients, two enzymes, each tab sealed in water-soluble PVA film. GECA certified, Sensitive Choice approved.
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Last reviewed: September 2026 · Koh Australia