Everything you need to know about phosphate-free washing detergents

Greywater can be a great reuse of water for your garden and lawns however as the water is untreated, everything that goes down the drain like household detergents, soaps or other chemicals that you use can end up affecting the health of your plants and soil.

Searching for environmentally friendly phosphate-free washing detergents is easy and a healthy choice for the environment.

Where can I find the phosphorus content of different washing detergents?

You can find a list of the salts, nitrogen and phosphorus content of washing detergents in Australia at www.lanfaxlabs.com.au and the Water Corporations website at www.watercorporation.com.au to help with choosing the product that is right for your family and the environment.

Why is the salt, nitrogen and phosphorus content in detergents and cleaners considered bad for the environment?

Salt is added to washing powders as fillers meaning there is generally less salt in concentrated powders and even less in laundry liquids. More salt in greywater can increase soil salinity which can affect soil structure by easily drying out.

Other minerals salts like calcium and magnesium can slowly accumulate in the soil and cause problems with soil permeability. This means that it becomes difficult for the soil to absorb water and plant roots drying out.

Soaps and detergents have a high pH which functions to dissolve grease and dirt. This can increase the soil pH resulting in plant damage and stunting plant growth.

Excess phosphorus content can be toxic to some plants, especially native Australian plants that are particularly phosphorus-sensitive such as Banksias, Grevilleas and Hakeas. Although the use of phosphates in laundry detergent was banned in Australia since 2014, it can still be present in dishwasher detergents.

Fats from soaps and fabric softeners can cause soil to become water repellent.

Harsh cleaning and household chemicals such as hair dye, nappy wash, disinfectants, bleach, eucalyptus oil, tea tree oil and germicides can affect the balance and health of microorganisms in the soil.

There is however a small benefit to the nutrients contained in greywater from laundry use. The phosphorus and nitrogen content from washing detergents can be substituted for the nutrients in fertiliser that help with plant growth. This means that greywater reuse on gardens and lawns can reduce the need for fertiliser application. Application of nutrients through the irrigation system also allows more even dispersion throughout the area and helps to reduce the chance of fertiliser runoff where nutrients can end up in waterways and stormwater drains.

Troubleshooting common problems caused by laundry detergents and cleaners

If you’re new to using a greywater system, it’s always a good idea to monitor your plants and lawns for at least the first six months. Look out for signs that your garden isn’t thriving with greywater reuse. Below are some common problems the use of laundry detergents and household cleaners that can be easily rectified.

Problem	Solution
Increase in soil salinity	Use a liquid or concentrated powder washing detergent containing less sodium
Plant damage caused by excessive phosphorus	Use a washing detergent low in phosphorus. Look for labels with “NP” to indicate that the product contains “No Phosphorus”
Soil exposed to high content of fats	Application of soil-rewetting agent every 6 months and avoid running high fat content products through the greywater system (divert to sewer)
Soil damage and plant toxicity	When using cleaning products or chemicals including bleach, hair dye, nappy wash, disinfectants (including eucalyptus and tea tree oil), don’t reuse the greywater and divert to sewer instead
Plants wilting or dying a particular area	There may be a blockage in the irrigation system caused by debris. For a subsurface system, flush the lines with clean water by removing the cap end of the distribution line. For a dripper system, pull the lines out of the ground and flush with clean water

Chemicals, salts and minerals in household cleaners and detergents can build up in the soil over time. By diverting greywater to sewer during the Winter season, it lets the soil “take a break”! The natural rainwater can gently flush out any accumulation of salts before the greywater system is ready to be used again in Summer time.

Be sure to check out our article on the top 10 tips you can follow to safely irrigate your garden with greywater.