Septic Safe Washing Machine Cleaner and Laundry Habits That Protect Your Tank

A septic safe washing machine cleaner is one you use at the label dose, once, in a normal cycle, and not on a day you’ve already put three loads through. The label matters less than the habit around it: “septic safe” is the manufacturer’s own claim, and what hurts a septic tank or AWTS is usually volume and repetition, not a single monthly clean.

The washing machine deserves more attention than the cleaner. It can dump a big slug of water, detergent, lint and sometimes bleach into your system in the space of an hour. Taylex’s owner’s manual for its ABS aerated system names harmful cleaning products and the washing machine as the greatest cause of problems.

This guide covers the water, the lint, the detergent, extras like softener and soakers, and how to clean the machine without knocking back the bacteria your tank depends on. For the wider list of household products, see what’s actually septic safe.

Why the washing machine matters so much

A septic tank is a settling chamber that needs time. The NSW Office of Local Government’s onsite wastewater guidelines say a septic tank should be sized to hold the peak daily flow for at least 24 hours, plus an allowance for sludge. That holding time lets solids sink and scum float before the liquid moves on to your absorption trench.

The same guidelines use a design allowance of 120 litres per person per day for a house on tank water, and 150 litres on town or bore water. That covers everything: toilet, shower, kitchen and laundry. Several loads back to back can push a big share of a day’s design flow through the tank in a couple of hours.

The guidelines warn that surge flows can overload a treatment system, cutting the time wastewater spends in it and potentially forcing untreated solids into the effluent application area. On a conventional system that means your trench. Solids clog the soil, and a clogged trench in clay is slow and expensive to bring back.

Spread the loads across the week

The most useful change costs nothing. NSW’s Easy Septic Guide, the state’s plain-English owner booklet, puts it first in its laundry tips: wash in stages over several days so you don’t flood the system with a large amount of water at one time. The Taylex ABS owner’s manual (V1.3, checked 28 September 2026) says the same for its AWTS: spread washing evenly over the week and avoid doing it all in one day.

In practice:

• One or two loads a day beats five on Saturday.
• Leave some time between loads rather than running them back to back.
• Don’t stack laundry on top of other heavy water use. Laundry, a dishwasher cycle and three showers in the same hour is the surge you’re trying to avoid.
• Fix leaking taps and cisterns. The Easy Septic Guide lists this in its laundry tips too; every litre that leaks goes through the tank.

The Easy Septic Guide also says front loading washing machines are best for households on septic systems, because they use less water and detergent.

Lint, fibre and the washing machine filter

Every wash sheds fibre from clothes and towels. Some settles into the sludge layer and fills the tank faster. Some stays suspended and heads for the trench, which is why NSW’s owner guide treats lint as a trench problem.

The Easy Septic Guide’s answer is simple: extend the life of your trench and avoid blockages by fitting a lint filter to the washing machine, and it notes that a stocking over the outlet hose will do. Check it every few loads and bin what it catches.

• Bin the fluff, don’t rinse it. Rinsing a lint filter or stocking in the laundry tub sends the fibre straight back to the tank.
• Separate the worst shedders. New towels and fleecy synthetics tend to shed the most. Running them in their own load with a filter on the outlet catches fibre at the source.
• An effluent filter backs it up. The Easy Septic Guide recommends having a plumber fit an effluent filter to the septic tank outlet to keep solids in the tank and extend the life of the trench. If your tank has one, we can check and clean it during a pump-out.

Septic safe laundry detergent: powder, liquid, sodium and phosphorus

Two ingredients in laundry products matter for a septic system: phosphorus and sodium.

Phosphorus is the waterway problem. The Easy Septic Guide says to always look for low-phosphorus or phosphorus-free detergents, because septic systems don’t work well with too much phosphorus going in, and phosphorus in waterways contributes to algal blooms and fish kills.

Sodium is the trench problem, and it matters most on a clay block. The NSW onsite wastewater guidelines list sodium from laundry detergents, soaps and cleaning products as a cause of damage to soil structure, and recommend laundry detergents low in sodium and phosphorus for that reason. Clay drains slowly to begin with, and damaged soil structure makes that worse. If your trench is already struggling, as covered in absorption trench failure signs, cutting the sodium in your laundry is one of the few things you control directly.

Powder or liquid? The Taylex ABS manual says liquid soaps break down more easily than powder, and to use only the amount shown on the label. So a liquid is generally the easier choice, but it’s a guide, not a rule: a low-sodium, phosphorus-free powder can be a better pick than a high-sodium liquid. Read the pack.

Fabric softener, bleach and nappy soakers

We couldn’t find NSW guidance that singles out fabric softener. Treat it like any other laundry chemical: it goes straight into the tank, it does nothing for treatment, and the less of it the better.

Bleach is different, and the manufacturers are direct. The FujiClean ACE owner’s manual tells owners not to put bleaches, disinfectants, whiteners, nappy soakers or spot removers into the system in large quantities via the sink, washing machine or toilet. Taylex’s manual says bleaches and harsh chemicals should only be used once a week and in small doses if required. Both are written for AWTS, but the principle holds for any system that relies on bacteria.

The Easy Septic Guide lists bleaches and disinfectants among the chemicals that can kill the helpful bacteria in a septic system. A measured splash of bleach in a whites wash now and then is a small, diluted dose. Soaking a tub of whites in strong bleach and draining it all at once is not.

Many nappy soakers are oxygen-based. We’ve covered what we could and couldn’t confirm about them in septic safe products. The short version: use the label dose, check the pack for septic or on-site system guidance, and don’t make it a daily soak.

How to use a septic safe washing machine cleaner without harming the tank

Front loaders especially build up residue and smells around the door seal and drum. The question is how to clean them without sending a strong chemical dose down the pipe.

What “septic safe” on the bottle means. It’s the manufacturer’s claim; we couldn’t find an Australian standard or certification behind it. Taylex’s manual makes a fair point: products labelled “greywater safe”, “septic safe” or “biodegradable” are safe most of the time, but many plant-based cleaners are powerful antibacterials, and a green label isn’t a guarantee. Look at what’s in it and how much you’re using.

A sensible routine:

1. Follow the machine’s manual first. It says which cleaning cycle to run and what can go in the drum, so you don’t damage seals or void a warranty.
2. Use one dose, at the label rate. Don’t double it because the machine smells.
3. Run it on a quiet water day. Clean the machine on a day with no other washing, not straight after three loads.
4. Don’t stack chemicals. A machine cleaner, then a bleach soak, then a load with extra softener is three chemical doses in an afternoon.
5. Wipe before you pour. Much of the mould and residue sits in the door seal, detergent drawer and filter. Wiping those by hand with warm soapy water cuts how often you need a chemical cycle at all.
6. Keep it occasional. Weekly chemical cleans are a lot of repeated dosing for a small benefit.

For benches and tubs, the Easy Septic Guide suggests traditional non-toxic cleaners like vinegar and bicarbonate of soda (it names the kitchen and bathroom, and the same logic applies in the laundry). Check your machine’s manual before putting anything like that through the drum.

Septic tank smell when doing laundry

A septic smell when the washing machine drains usually points to one of these:

• The tank is due for a pump-out. When sludge and scum take up most of the tank, a surge of wash water has less room to settle and can push solids on towards the trench. Other signs are in signs your septic tank is full.
• The trench isn’t absorbing. If the trench is saturated or clogged, a big load of wash water has nowhere to go, and you may smell it or see wet ground over the trench afterwards.
• A dry trap or venting problem inside the house. A dried-out laundry floor waste or a vent problem can let gas back into the house when water rushes through the pipes. That’s work for a licensed plumber, not a tank problem.

If spreading the loads doesn’t fix it, have the tank checked. A routine septic tank pump-out is $350 to $500 for a tank up to 3,000 litres (typically a 2 to 3 bedroom home), and $400 to $650 for a 3,500 to 4,500 litre tank. We quote the actual figure before we start.

AWTS owners: surges hit harder

An aerated wastewater treatment system has more working parts than a plain tank: an aeration chamber where a blower keeps aerobic bacteria working, a clarifier, a chlorinator and an irrigation pump.

• Stay under the design flow. The FujiClean ACE manual gives a daily design flow of 1,200 litres and tells owners to keep household water use well below the system’s daily design flow. A big washing day eats into that fast.
• Expect high water alarms after a surge. Taylex’s ABS manual says a high water level can be caused by several sources of water coming in at once and may correct itself: wait 15 minutes for the surge to stop and see whether the alarm stops. If it doesn’t, the manual lists checks on the irrigation filter, line and pump. Our guide to why an AWTS alarm is beeping covers the other causes.
• Older units may cope less well. The NSW guidelines say systems accredited by NSW Health against AS 1546.3:2017 are stress-tested for short-term surge flows and include features to manage them, and that earlier accreditations didn’t include these features as standard. If your AWTS is an older model, spreading your washing matters even more.
• The chlorinator isn’t a licence for bleach in the wash. Bleach from the washing machine reaches the bacteria in the treatment chambers long before anything gets to the chlorinator.

Your quarterly service is where a technician sees the effects: poor aeration, odd colour, sludge building faster than it should. If your authorised AWTS service technician suggests limiting a laundry product, take the advice; Taylex’s manual says a technician may do this even for a product it lists as suitable. You can book through our AWTS servicing page, or call 0468 278 123.

Frequently Asked Questions

Is septic safe washing machine cleaner actually safe for a septic tank?

“Septic safe” is the manufacturer’s own claim, and we couldn’t find an Australian standard or certification behind it. A single dose used at the label rate in its own cycle is a small, diluted load for an established tank. The risk comes from repeat doses, doubling the amount, or stacking the cleaner with bleach soaks and heavy washing on the same day.

Can I use bleach in the washing machine if I have a septic tank?

Occasionally and in small, measured amounts. NSW’s Easy Septic Guide lists bleaches among the chemicals that can kill the helpful bacteria in a septic system. Taylex’s owner’s manual says to use bleaches only once a week and in small doses, and FujiClean’s says not to put them into the system in large quantities via the washing machine.

Is powder or liquid laundry detergent better for a septic system?

Liquid is generally the easier choice, because the Taylex ABS owner’s manual says liquid soaps break down more easily than powder. What matters more is sodium and phosphorus, so pick a low-sodium, low or no phosphorus product and use the label dose, whether it’s a powder or a liquid.

How many loads of washing a day is OK on a septic tank?

There’s no official number, but NSW’s Easy Septic Guide says to wash in stages over several days so you don’t flood the system with a large amount of water at one time. One or two loads a day, with a gap between them, is a sensible target for most households.

Do I need a lint filter on my washing machine if I have a septic tank?

It’s a good idea and it’s cheap. The Easy Septic Guide recommends a lint filter on the washing machine to extend the life of your trench and avoid blockages, and says a stocking over the outlet hose will do. Empty it regularly and put the lint in the bin, not down the laundry tub.

Why does my septic tank smell when I do laundry?

A smell that shows up when the washing machine drains usually means the tank is due for a pump-out, the trench isn’t absorbing, or there’s a dried-out floor waste or venting problem inside the house. If spreading your loads doesn’t fix it, get the system checked.

Sources and further reading

• NSW Office of Local Government, The Easy Septic Guide: laundry tips (washing in stages, low-phosphorus detergent, lint filter, front loaders), the effluent filter recommendation, and bleaches killing septic bacteria.
• NSW Office of Local Government, Onsite Wastewater Management Guidelines (April 2025): design flow allowances, septic tank sizing, surge flows, sodium and soil structure, the detergent recommendation, and surge testing under AS 1546.3:2017.
• Taylex, Owner’s Manual: Taylex Advanced Blower System (ABS), V1.3, March 2026: the washing machine as a cause of problems, spreading washing, liquid versus powder, bleach use, the note on “septic safe” labels, and the high water alarm.
• FujiClean Australia, FujiClean ACE Owner’s Manual: the 1,200 litre daily design flow and the warning on bleaches, whiteners and nappy soakers.