vegetable patch design
Wicking Beds
how to build a wooden wicking bed - page 2

12.  cut hole and insert PVC outlet/observation pipe
  • Take a 400 mm section of 90 mm PVC pipe and cut a 20 mm hole near one end so that the edge of the hole is 7 cm from from the end of the pipe. 
  • Cut slots or drill holes at the 20 mm hole end of the pipe to allow water to flow into the pipe. 
  • Once you have done this hold the pipe upright with the 20 mm hole at the bottom  and push the 20 mm threaded tank outlet through the 20 mm hole so that the PVC pipe stands upright.
 Details of how to drill the hole into the pipe and cut the slots can be found in the Cut And Drill Outlet Observation Pipes section of How To Build A Plastic Tub Wicking Bed.
Photo of the inlet and outlet pipes in a wicking bed.
On the left is the 100 mm inlet pipe with T piece and Reducer to 50 mm T piece.  On the right is the 90 outlet/observation pipe.

Photo of the bottom of a wicking bed with agricultural pipe laid out.
50 mm agricultural pipe laid out in a loop.

Photo of stones layed out in the bottom of a wicking bed.
Stones added to a height of around 70 mm.

Photo of a wicking bed with weed matting layed out in it.
Stones covered with two layers
of non woven weed matting.

Photo of a wicking bed with soil added to it.
Wicking bed with soil added.

Photo of the side of a wicking bed with weed matting.
Woven weed matting folded
over and secured with screws.
13.  build inlet pipe with elbow and t piece
  • Take a 40 cm section of 100mm PVC pipe and connect  to a 100 mm T piece.
  • Where the T piece sticks out at right angles put in a 100 to 50 mm reducer.
  • Connect a 50 mm T Piece to the end of the 50 mm reducer so that the two ends of the 50 mm T piece stick out horizontally, 
  • Place the completed section next to the PVC outlet/observation pipe
I used 100 mm PVC pipe with a 100 mm T piece to allow enough space for a low pressure float valve to be inserted into it.  If you are not using a low pressure float valve than I suggest you use 90 or 75 mm PVC pipe with an elbow instead of a T piece. 

You could even use all 50  mm pipe and do away with having to use a reducer, but this would mean you would have a very small inlet for watering.
14.  Lay out Drainage pipe and cover with stones
  • Attach a length of 50 mm agricultural drainage pipe to one end of the 50 mm PVC T piece. Then snake it around the bottom of the wicking bed and attach the other end to other side of the 50 mm T piece.
  • Spread stones evenly across the bottom of the bed to a height of around 7 cm.
I used bricks both to hold the agricultural pipe in place and to measure the height of the stones.  As a brick is 7 cm high I filled the bottom with stones to the height of the bricks then simply removed the bricks and filled in the holes left by the bricks.

15.  Cover with weed matting and fill with soil.
  • Cover the top of the stones with two layers of non woven weed matting.   Where the PVC pipes stick up cut holes in the matting and push it over the tops of the pipes.
  • Fill with friable soil until nearly full.

The weed matting is to stop the soil from mixing with the stones as water has to move freely through.  So it is important to tuck the matting right up against the walls of the bed.  You could probably get away with one layer of weed matting but as it is relatively cheap I thought it was worth using an extra layer just to make sure.

For the best results the soil needs to be friable sandy soil.  Heavy clay soils will not do.  If your soil is heavy then mix it with sand and mulch to make it more friable.

16.  tack sides and top up with soil
  • Fold over the woven weed matting and tack it to the sides using 13 mm button head needlepoint screws.   If the end of the weed matting is too long then cut some of it off before folding it.
  • Top up with a bit more soil
I didn't tack the weed matting until the very last as the adding of the soil created a bit of settling and movement of the matting.

You now have a finished wicking bed.

This design proved very successful. 

The only thing I would definitely have done differently is use an extra four landscape nails to nail the bottom and top sections of the walls together as there was some miner lifting at the corners due to the aging of the timber.  Using some extra nails would probably have stopped this.

But it  also might have been wise to put down a few centimetres of fine sand before laying out the pond liner, which is standard practice when building a conventional pond.