Can I Use Washing Up Water On Plants

If you’re looking to save water and money, you might be wondering, can i use washing up water on plants? This greywater, from washing dishes, can be a resource for your garden, but it must be used carefully. Using it incorrectly can harm your soil and plants. This guide will walk you through the safe practices to make this work for you.

The idea is simple: reuse water from your kitchen sink to irrigate. It reduces your fresh water use and can provide some nutrients. However, it also introduces soap, grease, and food particles. Getting the balance right is key to keeping your garden healthy.

Yes, you can, but with important conditions. It’s not as straightforward as tossing any soapy water on your flower bed. The safety depends entirely on what’s in your washing-up liquid and what’s on your plates.

What is Greywater, Exactly?

Greywater is gently used water from bathroom sinks, showers, and kitchen sinks. It’s distinct from blackwater (toilet waste). Kitchen greywater is often the most challenging because it contains fats, food residues, and stronger cleaning agents.

The Potential Benefits for Your Garden

Water Conservation: You significantly reduce your household’s demand for fresh water, especially valuable in dry seasons or drought areas.
Nutrient Source: Small amounts of food particles can break down and add organic matter to the soil.
Cost Savings: Lowering your mains water usage can reduce your utility bills over time.

The Real Risks You Need to Know

Ignoring the risks can lead to serious garden problems. The main concerns are:

Salt and Chemical Buildup: Many detergents contain sodium, boron, and chlorine. These accumulate in soil, damaging its structure and poisoning plants.
Harmful Bacteria: Water from washing raw meat, dirty nappies, or pet bowls can contain pathogens like E. coli.
Fat and Grease Blockage: Oils can coat soil particles, creating a water-repellent barrier and reducing air flow to roots.
pH Imbalance: Strong soaps can make soil too alkaline, locking away essential nutrients from plants.

Choosing the Right Washing-Up Liquid

This is the most critical step. Standard dish soaps are designed for cleaning plates, not nurturing soil. You must choose carefully.

Avoid: Detergents with boron, bleach, petroleum distillates, sodium salts, or artificial dyes and perfumes. These are often listed as “antibacterial” or “powerful grease cutters.”
Seek Out: Plant-based, biodegradable, and low-sodium soaps. Look for brands marketed as eco-friendly or greywater-safe. Castile soap is a popular, simple option.
Simple Test: If a soap is safe for hand-washing delicate fabrics or babies, it’s a better bet for plants. But always check the label.

What NOT to Put in Your Sink

If you plan to reuse the water, you must change your washing-up habits. Avoid putting this water in your collection bucket:

Water used to rinse raw meat, fish, or eggs.
Water with heavy milk residue.
Water from washing pet dishes or soiled cloth nappies.
Water with strong chemical cleaners, like oven cleaner or bleach.
Water from washing very greasy pans (wipe out excess grease with kitchen paper first).

A Step-by-Step Guide to Safe Application

Follow these steps to minimize risk and maximize benefit.

Step 1: Collect the Water

Use a basin in your sink or a dedicated bucket. Don’t use water that has been sitting for more than 24 hours, as bacteria can multiply quickly. Apply it to the garden the same day.

Step 2: Cool and Settle

Let the water cool completely. Allow food bits to settle to the bottom. You can gently pour the water off the top, leaving the sludge behind. Dispose of the sludge in your food waste or trash.

Step 3: Apply Correctly

Never use a sprayer or sprinkler, as this can aerosolize bacteria. Pour the water directly onto the soil at the base of the plant, avoiding the leaves and stems. This delivers water to the roots and prevents leaf scorch from soap.

Step 4: Rotate and Observe

Don’t use greywater on the same plants every time. Rotate between greywater and fresh rainwater or tap water to prevent salt buildup. Watch your plants closely for signs of stress, like yellowing leaves or stunted growth.

Best Plants for Washing-Up Water

Some plants are more tollerant than others. It’s best to start with these hardy varieties:

Established Fruit Trees: Their large root systems can handle variations better.
Ornamental Shrubs: Like lilac, rose, and buddleia.
Hardy Perennials: Such as daylilies or ornamental grasses.
Lawns: Can be watered with diluted, settled greywater.

Plants to Avoid

Never use greywater on these more sensitive plants:

Seedlings and young plants (their roots are too delicate).
Acid-loving plants (e.g., azaleas, rhododendrons, blueberries).
Leafy vegetables you eat raw (e.g., lettuce, spinach, herbs).
Root vegetables (e.g., carrots, potatoes).

Long-Term Soil Health

To counteract any negative effects, you must care for your soil proactively.

Add Compost Annually: This improves soil structure, helps filter impurities, and supports beneficial microbes.
Mulch Heavily: A thick layer of organic mulch (wood chips, straw) helps slow evaporation and protects the soil surface.
Get a Soil Test: Every few years, test your soil’s pH and salt levels. This tells you if you need to adjust your practices or add amendments like gypsum.

Simple FAQ on Using Dishwater in the Garden

Is all biodegradable soap safe for plants?

Not necessarily. “Biodegradable” means it will break down eventually, but it may still contain salts harmful to plants. Always look for greywater-specific or garden-safe labels.

Can I use water from washing clothes?

Laundry greywater is often easier to manage if you use a plant-friendly, low-sodium detergent. Avoid water from washing nappies, oily rags, or with bleach and strong softeners.

What about pasta or vegetable cooking water?

This is excellent for plants! Let it cool, and pour it on. It contains small amounts of nutrients from the food. Just ensure it’s unsalted.

Is it safe for edible plants?

The general advice is to avoid using it on edible parts of plants, especially roots and leaves you eat raw. If you do, use only the safest soaps, apply to soil only, and allow a long time between watering and harvest. Many gardeners reserve it for fruit trees or ornamental plants only.

Will it attract pests?

If you pour out large food chunks, it might. That’s why careful collection and settling is so important. Always pour clear water onto soil, not leaving food scraps on the surface.

Using washing up water on plants is a practical way to be more sustainable. It requires a mindful approach—choosing the right products, adjusting your habits, and observing your garden closely. Start slowly, perhaps with one or two robust shrubs, and see how they respond. With these precautions, you can turn an everyday waste product into a valuable resource for your garden’s health.