A Home for Koi

DIY Koi Pond

completed koi pond

What You Need For the Koi Pond

1 pond (10 000 litre koi pond)
1 filter system
1 bottom drain
3 m x 110 mm PVC pipe
1 m x 50 mm PVC pipe
1 stainless steel rim flow (400 mm)
3 x 110 mm PVC 90° elbows
2 x 50 mm PVC 90° elbows
3 m x 22 mm tubing
1 T-piece for tubing (22 mm)
1 reducer from 50 mm to 22 mm (tubing size)
2 control valves
1 male fitting with nut (22 mm)
PVC weld
Marine silicone
River sand (for marking, bed and backfilling)
UV light

Edging of the Pond

13 concrete sleepers (or enough to cover outer edge of pond)
6 bags building sand
1 bag cement

Splash Wall

30 x M190 blocks
6 bags building sand
1 bag cement
2 bags tile adhesive
Wall cladding (to cover splash wall)
6 bags concrete stone
5 bags river sand


Long spirit level, spade, pick, cordless drill and 6 mm drill bit, small angle grinder with steel cutting disc and a masonry cutting disc, flat screwdriver, bricklayer’s trowel, serrated trowel, block brush, plastic builder’s bucket

koi pond diagram

Inserting the Pond

inserting the koi pond

1. Clear and level the area. Position the pond upside down exactly where you are going to install it and mark around the edges with river sand. Remove the pond and excavate to the correct depth and shape. The pond should sit comfortably in the excavated area, with the edge level with the ground. Test the pond’s fit, then remove for plumbing.

koi pond filter system

2. Position the filter system so that the water level within it will be the same as that in the pond. Mark the position with river sand, and excavate. Plan the bottom drain piping from the pond to the filter and then the pipe from the filter, through the UV light and via control valves, to the two pond inlets, and excavate where necessary. (See sketch.)

3. Mark the position of the bottom drain in the pond and cut out using the angle grinder. Place the drain attachment ring around the drain hole and mark for drilling holes. Drill all the holes. Apply silicone to the underside of the ring, position the drain and screw the ring into the pre-drilled holes in the bottom drain. Remove any excess silicone from the bottom drain ring.

4. Lay out the piping from the bottom drain in the pond to the filter using 110 mm PVC pipe and fittings. Spread and compact a layer of fine river sand in the  trench as a bed for the piping. Spread a layer of fine river sand (± 80 mm deep) in the bottom of the entire excavated area for the pond. Compact the sand and level it out.

5. Slowly lower the koi pond onto the level river sand and once in position connect the bottom drain to the piping. Quarter fill the pond with water, then backfill the gap between the excavation and the pond’s edge. Add more water to the pond and then backfill further. Run water onto the backfilled soil to encourage it to fill and flow into all areas around the pool. Continue until backfilling reaches ground height.

HINT: Fill the pond bit by bit with water
as you backfill around the pond’s
outer edge to prevent the pond from
bulging out of shape.

Building the Splash Wall

6. Excavate behind the pond for the splash wall’s foundation, 300 mm x 150 mm deep, making the wall as long as the side of the pond. Mix 4 parts stone, 2 parts river sand and 1 part cement with enough water to make a fairly wet mixture. Fill the foundation to just below ground level and leave to dry for 3-4 days.

7. Mix 6 parts building sand to 1 part cement and water for the mortar mix. Lay three rows of blocks and then place the stainless steel rim flow in the centre of the wall. Build the last row of blocks over the flow. Allow the wall to dry for a few days.

8. Using tile adhesive, clad the wall in rows from the bottom up. Clad the sides and top of wall in the same manner. If you want a neat appearance, plaster or bag wash the back of the wall.

Edging Around the Pond

9. Mix 4 parts building sand to 1 part cement and some water until your mix looks like thick yoghurt. Spread a generous amount around the edge of the pond and
place the sleepers in position. Remove any excess cement from the sleepers before it dries.

10. Hook up the filter, UV light, T-piece and control valves to the pond inflow and then the bottom drain pipe to the filter. If you use a secondary inlet, drill a
hole near the top of the pond and connect it using the male fitting with nut. (See sketch on previous page.)

The Gardener