Considering the burgeoning global human population, water will be one of the scarcest – and therefore most valuable – commodities.

On our farm, we have converted a massive old shed into a housing unit, and ‘grey’ water from the kitchen and two bathrooms has been channelled into the adjoining vegetable garden that supplies us and our employees with a variety of fruit, vegetables, and herbs.

In undertaking this water conservation project, I used 40mm PVC plumbing piping that exits the building and has been laid/buried just under the surface of the garden beds. Pipes, which will eventually be hidden from view, irrigate the soil via 6mm holes drilled at intervals of 10cm to 15cm.

A wood or steel drill bit works quite well. Take care when drilling to avoid injury.

Important considerations

The pipes are not level but lie at a slight rather than steep gradient; obviously, in the direction that you want the water to flow and to irrigate. If too steep, the water runs too rapidly through the piping and dams at the lowest end.

I block the ends of the pipes to keep the water in them and perpetually exiting through the drilled holes that should face downwards. A few holes can also be drilled along the top of the piping at intervals of about 60cm to help break the vacuum.

Also of importance is that the furrows in which the pipes are buried must first be lined with smallish stones to a depth of about 8cm to 10 cm. The stones can be of the ironstone variety or the quarry stone used in making concrete.

Rinse the stones to remove dust, as this can block the aforementioned holes and/ or prevent water from seeping into the surrounding soil. Use stones about the size of a golf ball and others half that size at a 50/50 ratio, because you want to create air pockets between the stones.

This stone foundation allows water to percolate outwards into the beds, and these stones and their surrounding air pockets have a filtering effect to ensure that clean water enters the underground water system.

After the piping is laid onto the stone beds, I add a few more stones onto the pipes to just cover them, and then I cover the lines with narrow strips of heavy-duty plastic damp course that prevents soil from filling the air spaces between stones.

After laying the plastic, I cover the pipelines with the soil that was originally excavated, and then lightly compact it. There are also environmentally friendly materials specifically made for pipeline protection. This porous material called ‘bio-cloth’ is sold at hardware stores and nurseries.

Remember, too, that when joining pipes, use a good-quality PVC cement that will prevent joins (elbows and T-pieces) from pulling loose.

Include stakes in the ground or paint markers on a nearby wall, as these will show you where the pipelines run after the final covering of the system. This will help prevent damage to the piping from garden forks or shovels in future.

A row of bricks or stones can be laid to mark the ‘mother line’ – the main pipe exiting the building, where offshoot pipes that enter your garden beds connect. This marking also prevents this main pipe from being damaged during future spadework.

So, rather than incurring huge costs to install drain fields, French drains, and/or septic tanks in localities without municipal infrastructure, I’ve created a multipurpose system that conserves water while also helping to produce valuable food.

However, it is important to remember not to make garden beds too close to a building (about 4m to 6m away is what I work on), as this can cause rising damp in walls.

While using water from basins, baths, showers, and sinks for irrigation is my priority, one should be weary of using water from clothes washing, as this could contain high levels of detergent that could affect soil, underground water systems, and plants.

If you live in an urban area, you should enquire about municipal or environmental laws that are specific to wastewater flow and usage. Also find out if there are any submerged electricity cables, sewerage lines, or clean water lines in the area that you wish to create this irrigation system and surrounding beds.

Try to make your system as uniform as possible. Don’t have one irrigation pipe lying much deeper or having more gradient than the others, as most water will flow down this pipe, and the others will be starved of water.

Shane Brody is involved in an outreach programme aimed at transferring skills
to communal farmers.