Food Garden · Homesteading · Off Grid · Water Supply

Water: Rain & Grey water collection & storage

Water Gathering Techniques

African rain on tiles

Now, when you start a veggie garden, ensure that you have access to water that is essentially free of charge. This will save you money and will not pull from valuable municipal water resources, especially when you live in semi-arid and arid areas (such as South Africa).

Collecting Rainwater

Rain cloud dark lightning purple black blue night
Now I have read lots of both great and horror stories on rain water collection – as long as the roof you choose is fairly clean (from leaves and twigs) and does not house birds (diseases are carried in bird feaces) the water is fine for vegetable watering. Our roof is kept clean by the wind and does not gather any other debris. Also the birds do not have suitable nesting sites on the roof – too hot up there! We have invested in a rainwater tank (since 2011) for the veggie garden that collects the rain that gathers on the roof of our house. Jojos and Flo-tanks are ideal with black inner linings to keep algal and disease growth to a minimum.

We started with a 1000 L rain water tank that was be easily filled in a 20 min thunderstorm. Since then we have upgraded to a 10 000 L tank at the main veg patch, a 5000 L tank at the pumpkin patch and the 1000 L has been moved to the front of the garden. The 5000 L is always full because of the sloped roof it is connected to (I think we estimated it gets 1000 L per 10 mm of rainfall). The 10 000 L tank gets 500 L per 10 mm of rainfall. Thus is takes 50 mm of rain for the 5000 L to be full and 100 mm of rain for the 10 000 L tank. We use about 1000 L of water a week for the veg gardens in summer, so we need 10 mm of rain a week to keep the tanks full (ha! like that will ever happen in SA! ) or  ~30 mm a month in summer to keep us going. So rain provides us with all of our water requirements during the summer months – given the summer rains aren’t too late in the season. It was touch-and-go a few times during our worst drought years (2014-2018) since 1942!

FloTek 1000L rainwater harvesting collection tank
Rain water tank and two 120 L drums with additional rain water

There are several way to use rain water:

✓ Watering the garden.
✓ Maintain the pool or garden water features.
✓ Washing or cleaning of items/surfaces in and around the house (windows, floors, showers, toilets, cars, outdoor containers, gardening tools…).
✓ Rain water collected from a clean roof can be treated for consumption: See the affordable OneDrop product (R 89.99, 30 ml can purify up to 600L of water), which can clean water from nearly any source and has been made by our own Council for Scientific and Industrial Research (CSIR-SA).

Grey Water

During winter, we have four 120 L drums, which we fill with ‘grey water’. Now I am going to dispel some grey water myths – you can water the entire winter with grey water from the washing machine. Some articles claim that it is not good to use grey water for extended periods and that it may harm plants due to chemical accumulation… We use the water from the second rinse cycle and there are washing powders commercially available these days that contain little phosphates to no phosphates. Also most of the chemicals will degrade in the environment due to the sun and weather conditions – the drums remain in the sun (not for more than three days), which assists with chemical degradation and the rest is degraded in the soil. The soil and plants are quite robust, so as long as you’re not pumping in industrial grade waste into the garden – the natural processes will compensate for the minimal increases in chemical levels in the soil. We use grey water exclusively on the ornamental plants in the garden, especially in winter and when the rain is a bit scarce in summer. You can also treat your grey water biologically prior to use.

Grey water refers to water from the washing machine, shower, rinse water ect. Black water, is what you do not want to add to your garden, refers to water from the toilet, dish washing machine, shower water containing hair dyes and any other water with food oils or industrial chemicals (paints, thinners…).

There are many places to collect grey water from:

✓ We also gather ‘grey’ rinse water such as the water from washing the vegetables from the garden, as the soil clogs the drain anyway.
✓ The cold water that runs through the pipes before the warm water starts to flow.
✓ Fish tank water  – contains lots of good stuff for the plants.
✓ Water you cooked any plant-based food in, veggies or pasta.
✓ The water that has become unsuitable-for-pet-consumption from the pet’s bowl.
✓ Water from the flower vase, after the flowers have died.
✓ Used water from mopping the floors/washing the car even.

It is quite amazing the amount of water you can actually reuse.

Water pump garden ornamental plants wall

Maximising water usage

The best solution for maximum water usage is to install a drip system, preferably an underground system – with a timer if you don’t want to water the garden yourself. Sprinklers and hose-pipe watering should be avoided as they use a lot of water and additional water is lost by watering the pavement or as mist/evaporation…

The drip systems available here in SA are not large enough for my garden and very expensive for my small gardening budget! So I am stuck on old fashioned watering-can methods. Although this can be tiresome, it is a good workout and you get to inspect the plants while you water them.

For my large plants and pot plants, I have invested in some ‘waterers’. These are ceramic based water holders and plant roots can pull upon the water they hold when needed, which is facilitated by the porous nature of the ceramic. They come in a large variety of shapes and sizes. You do get huge ones that can be sunk into the garden known as ‘ollas’. There are ceramic spikes available that you attach to plastic coke bottles (so more water can be stored in the waterer), wick systems and self-watering containers. These are also useful for holiday watering.


Mulching is another way to maximise water usage. My previous views on mulching was that the mulch has the ability to hide very large weeds, protects some pests, feeds termites (wood/bark based mulch) and I also felt that it made the garden look like a dump. Putting old reservations aside I have decided to give grass-clippings mulch a try, but since have moved on the living mulch (post coming soon!).

Mulching gives the following advantages:
✓ Retains soil moisture
✓ Retains heat in winter
✓ Cools the soil in summer
✓ Watering intervals are reduced
✓ Weeds are blocked from the sun and are kept at bay
✓ Harbour beneficial insects
✓ Adds additional nutrients to the soil

So a good carpet of dry mulch, 1-3 inches, should be applied to the soil around vegetables and plants. Mulch should not reach the stems of the plants, as they may induce rot. Generally anything can be used for mulch; leaves, compost, grass clippings, old carpet… I used grass-clippings, since they are free and ever abundant from mowing the lawn. Mulching can reduce watering by up to 70%.

Here are some guidelines for using grass-clippings as mulch:
✓ Dried or already decomposed grass-clippings are preferable. Green clippings produce a lot of heat and nitrogen during initial degradation that may harm plant roots – a small layer of 1 inch green clippings can be used with no adverse effects.
✓ A good 3 inch mulch keeps down weeds
✓ As the grass-clippings decompose, they release lots of nutrients, especially nitrogen. Nitrogen is good for leaf and root formation and you lettuces will appreciate the boost.
✓ Grass-clippings should be mowed into short pieces, to minimise compaction during decomposition.
✓ Grass-clippings should be used for herbicide or pesticide-free lawns as not to harm your vegies or beneficial insects.

Water wise vegetable gardening in South Africa

There are 45 countries listed as water poor with 35 being in Africa. South Africa is ranked 27th with an average rainfall of 492 mm per year. This is half of the world average at 985 mm per year. South African is predicted to become water scarce by 2025! Most of South Africa’s water is used in agriculture (60%) and by having your own vegie patch you save on water. Not only is it better for the environment, due to less fertiliser and pesticides that are used, but you negate the packaging -, transport -, storage costs and water wastage associated with getting vegetables at the grocer. Additional water saving will not only save money, but will reduce the stress on water supply in South Africa.

Water wise rand water logo south africa

Here is a table, provided by Rand Water, of the amount of water used by certain vegetables/fruits:

Vegetable water use Leaf vegetables Root/Stem crops Fruits & Legumes
High Lettuce Leeks Cucumber
Watercress Asparagus Squash & Pumpkin
Swiss Chard & Spinach Spring Onions Tomatoes
Rocket Celery Eggplant
Medium Parsley Rhubarb Peas
Broccoli Peppers
Brussels sprouts Beans
Low Cabbage Cauliflower Most herbs
Water from tap drops
Fresh water is a precious commodity and water shortages are becoming the norm  – one day wars will be fought over a few handfuls of fresh water

National Water Week: 17-23 March 

National water week from 17-23 March aims to bring awareness to your most precious source: WATER. You can find out more on how to save water and alleviate the strain on our water supply at Journey for Water.

The following images were generated from the Journey for Water site and therefore copyright belongs to them. Here are the sources of water for Roodepoort and the surrounding area: Northern Drakensberg and Maloti Drakensberg.

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Please see my #ThinkWater post for move water conservation tips in and around the house/office as well as a challenge to everyone to get your water usage to 50 L pp/day!



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