Self-watering Bathtub - Easy to Make, Easy to Grow Food

Self-watering bathtub 

When I found a bathtub on the side of a road, a bright idea came to me - it could be a great self-watering garden bed! The challenge would be to create a raised floor for holding soil above and storing water below while allowing water transfer between the water storage and the soil. I have come across a lot of different bathtub designs using woodchips, gravel or sand for water storage but they significantly reducing water holding capacity and at the same time are bulky and fairly heavy. So I came up with a design using a few recycled materials to create a self-watering bathtub with a massive water storage capacity of  about 100litres.

The self-watering bathtub has turned out to be very successful for growing our vegetables specifically water loving plants such as cucumbers and melons. The massive water holding capacity provides a constant supply of moisture to plants (via a wicking effect) with no need for watering for several weeks even months. It makes growing vegetables easy and bulletproof. More importantly, the self-watering bath tub is easy to make from materials readily available.


Materials needed:

• a recycled bath tub,
• three bricks
• a piece of steel mesh/old rigid fence
• a couple of hessian bags/ old towels
• a piece of PVC pipe about 60 cm long

Step by step to make a self watering bath tub:

Raised floor - Steel mesh on bricks 

1. Seal the bath drain with a plug.
2. Place three bricks on their edge into the bathtub (one at each end and the other in the middle of the tub).
3. Cut the steel mesh (a concrete reinforcing mesh or an old fence panel) to fit into the bathtub and rest it on the bricks creating a raised floor.
4. Use hessian bags/old towels to cover the steel mesh with hessian ends reaching down, into the bottom of the bathtub. The hessian will hold the soil and provide wicking from the ends. (You can add a shade cloth under hessian bad which holds soil better and last longer.)
5. Drill a overflow hole into a side of the bathtub level with the raised floor.
6. Cut a piece of pipe (about 60cm long) and stand it so it runs from bottom to the top of the bathtub, to be used to fill the lower area with water.
7. Fill the bathtub with rich organic soil.
8. Plant seeds or seedlings.

Hessian bags on mesh with ends in water

9. Mulch it!
10. Water it well from the top and fill up water storage.
11. Make a float (a piece of styrofoam and a wooden skewer) of a smaller diameter but the same length as the pipe and place it into the watering pipe to indicate water level.


An alternative way of making the self-watering bathtub is by using plastic crates or a wooden pallet.
Cut a PVC pipe of the same length as a crate/pallet height . Glue (adhesive sealant) the pipe into the drain hole at the bottom of the tub with the top of the pipe sticking out into bathtub (about level with the top of the crate/pallet. Make sure it is properly sealed, so water is held in the bathtub up to the top (about 20cm) of the PVC pipe. (If there is more water in water storage it overflows through the top of the pipe and get out the bathtub drain.) Then place plastic crates up-side down to create huge pockets for water storage. Note you can use anything which would create raised floor (eg. wooden pallet). Cut a watering-in PVC pipe so it comes from bottom to above the top of tub and secure it in a corner of the bathtub. Cover crates with shade cloth which goes up and down on the perimeter of the bathtub and between crates creating pockets. Fill pockets up with soil which will become a wick. Fill the entire tub with rich organic soil.

Mulch it on the top to stop any surface moisture evaporation and plant seeds or seedlings. Water it from top for a week or two so soil will settle down and an effective wicking effect is established. Place a bit of styrofoam float with wooden skewer into the watering pipe and fill it in with water until it's full and starts to flow from the bottom.

The trick of growing healthy plants is to keep them stress free. If they have enough nutrition, the right soil temperature (not too hot) and a constant supply of moisture especially on hot summer days, they will thrive. This can be easily achieved with the self-watering bathtub. Nutrition after heavy rain can be recovered from the water storage which also keeps soil cool, via an evaporation effect - without loosing water. The constant on demand, water supply via a wicking effect make plants happy even during hot summer days.

The self-watering bathtub is great to use everywhere: at gardens with bad soil or trees roots sucking all nutrition, concrete yards, balconies etc. We found them great for growing our food as they really, really work.

Happy gardening