DIY KOI Pond – Part 3 – Plumbing


and now the part I was really looking forward to do – Plumbing and Filtration.

This task was something I had never even tried before, knew nothing about it and as a new challenge I was really keen to give this a try. I again took advise from the KOI pond suppliers and internet for the basics but even the professionals were intrigued in that as a first time try I wanted to incorporate the ability to include a “Waste” option in my design so I could partly empty the pond if needed, and this turned out to be very handy.

So for the size of the pond (2340l) it was recommended that I get a BioFilter “CB4”  which turned out to be a big plastic box with a pipe coming in the top, sponge and some type of shredded plastic BioFilter material inside to support the Biological growth and a pipe from the bottom but coming up to midway to control the flow of the water, works something like a toilet U-Pipe. They also recommended a 15W UVLight to control Alge, and with the KZN, SA hot long sunny days this is a good call.

Inside of the CB4 Filter Box

Inside of the CB4 Filter Box

Now as I said, I  have never done any sort of plumbing before but I was certainly not going to make the design easier. Because I also had a waterfall and the water coming out of the BioFilter is not under pressure, ie comes out under gravity I either needed to

  1. 1)Put this great big ugly green BioFilter on top of the waterfall,
  2. 2)Use 2 pumps one for the Biofilter / UVLight and one for the Waterfall
  3. 3)Use one bigger Pump and split the water

Well 3 sounded like the way to go so I ended up getting a 6000 l/hr pump so I could feed about 3000 l/hr to the Filtration system and the rest to the Waterfall. Here my concern was that I had no idea how much water the waterfall could handle, too little and it would look silly, too much and it would overflow/splash out of the runs, but it was recommended that you should turnover the pond volume every hour though the filter and the 15w UV light could not handle more than 3000 l/hr so basicaly I was stuck at splitting the water flow in 2.

So this meant I needed 2 Values to regulate the flow to the filter and waterfall, 2 were recommended so you could manage the flow better, only using on means you are  regulating the water based on least resistance, ie water will try take the flow of least resistance, and if your one path has no resistance, ie is big enough to handle the full volume the path with the valve on even if it is fully open won’t force the water down it. So you basically pump the water out of the Pond, use a “T” piece to split the water and put a value on each line, and this way you can create resistance on each line separately and have finer control over how the water splits, not to mention the ability to segment a run if there is maintenance required.

I however wanted to have the ability to “Waste” the water in my pond so I split the run into 3 with values on each. 2 to Split the water for the Filtration and Waterfall, and one to “Stop” the water from going to waste.The Pond people were intrigued at this design, they normally just use multiple pumps. Now while this has its advantages, ie you can completely turn off the waterfall and leave the filer going without sending too much water through it seemed wasteful to me and also not realy “elegant”.  I had no concerns about the waterfall making too much noise as it was not that close to the house.

I also decided to use 50mm PVC piping throughout the whole design except for the connections to the pump and Waterfall hose. The main decision here was that the UV light and BIO filter already had 50mm couplings on it and I would also not then have to worry about stepping up and down and causing possible pressure differentials, again messing with the resistance paths. PVC is also the obvious choice as it is easy to work with.

Now the theory and drawing of the layout was easy but when you want to fit all the valves and connections in as smaller space as possible, that was where the challenge came in..That was until I realised I should be thinking in 3D. Now for a plumber this is probably considered “obvious” but for someone with no experience in this area was like a lightbulb moment!

Pond Plumbing

Pond Plumbing

Measuring the lengths of Pipes and getting the angles and connections just right was soooo much fun, it was a blast trying to get this just right so everything fitted neately.

So with everything together I switched on and held my breath. Would everything just burst apart with water coming out everywhere? Would I have to redo everything? Did I put enough glue on? What did I not know that I should have done?

Well, everything I put together myself worked perfectly, but almost every part I bought did not!. The UV light did not work and I had to take it back, The BioFilter Leaked and had to take it back twice until they finally replaced it, but the suppliers were good in this respect, as they went out of their way to try repair and where they could not they replaced it without any grumbles.

I then used a rock shaped pool pump cover to hide the filter box,

Side View of CB4 Filter

Side View of CB4 Filter

So what did I learn…

  1. 1)Ask advise and ask lots of questions, do allot of planning and thinking before starting.
  2. 2)Ensure that you use a “removable joint” (a connector that can unscrew without turning the pipe on either side of it)for both in and out of the BioFilter – the one I had, had a Joint on the In Pipe already but not on the out pipe. I originally just glued a pipe into the out side but when I found the Filter was leaking I had to cut it out of the pipe run. I retro fitted it with a joint but the alignment was very tricky. I reccomend that you do it like this from scratch. There will be times you may have to remove the filter for repairs in future and this will save a lot of stress later. The UV light already came with joins on both sides so this was already removable. It may be a good idea to put removable “joints” at key points along the layout so you can dismantle later of needed. Not sure if this will ever be needed but a thought. The Valves I used came with this ability already so I can take my pipe runs apart in most places if needed.

3)Pay attention to the values, the ones I got, Ball valves which are very good at regulating and even stopping the water, were directional, which means water should flow though it in a certain direction, look out for the arrow indicating the direction of the flow.

4)Measure twice and cut once!!! This goes for everything but really counts here. Also go slowly, cut one piece, roughly fit it, Glue the connectors on let, it Dry (takes about 8 mins before you can safely handle it) Fit it and then start the next Piece

5)Try keep all the joins and connections above ground, I accomplished this by keeping these all around the Filter and where needed, try use long pipes for the run. This way you reduce the possibility of underground leaks that you may not notice or will have difficulty repairing, if the connections leak above ground by the filter you will notice and repairs will be much easier

6)You may be tempted to try fit the connections and the pipes together so you can assemble with the idea of taking them apart later for gluing, I found this impossible, the connections were so tight already you could not get them apart again. This makes the Measure twice, cut once a real mantra

7)When cutting take into account the amount of pipe that is going to slide into the connector, in my case it was 3cm so had to account for this on either side.

8)Once I had put everyting together I read that you should try design to ensure the water flows and there are no deadspots and that you don’t just end up filtering already filtered water. So don’t situate your return pipe from the BioFilter right next to where the Pump draws water otherwise you are dumping filtered water right by the pump. Try situate it away from that area if possiable and at a minimum you need to move water to the other side of the pond from where the pump is situated. I was ok with this cause I split the water and move half to the waterfall on the other side of the pond. It does not have to be filtered water, just as long as you cause some water flow.

9)I also read that you should house your pump in a plastice Plant basket to reduce “gunk” getting into the pump. Later I saw another pond where not only did they house it in the Planting basket but they also covered it over (ie sealed in in with just the pipe comming out the top) with shadecloth type material. This competely prevents Leaves

10)I also read that you should put the Pump on Bricks so it raises it from the bottom, this also prevents gunk that forms at the bottom from getting into the pump but also if there happens to be a leak it won’t empty the whole pond while you are away and so hopefully save your fish. I later found other diagrams on the net to prevent complete emptying of the pond should there be a leak in other cleaver ways. With the pump on the bricks it also increases your Head hight – basicaly how far the pump can pump water cause it is not so deep. You can easily reach it from the surface without getting too wet to remove leaves etc.

Hope this has been helpful, leave some comments a questions and I will try answer from my experience.


About mikegsworld

Just a Computer geek who has 2 wonderfull kids, wife,Rat Dog, Rabbit and some Koi. I Enjoy Fishing - esp. Freshwater Fly but starting to play with Salt Water Drop Shot. Enjoy making things and general DIY

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