How To Build A Koi Pond With A Bottom Drain

a few koi fish swimming in a koi pond

As Koi ponds are growing in popularity, more and more people are starting to build them in their gardens. Many people opt to build their own Koi ponds as a simple pond is easy to build. But how do you build a Koi pond with a bottom drain?

If you are building a Koi pond yourself, buying a bottom drain kit is highly recommended, as this will ensure you have all the parts required for the drain, making the installation easier. We will cover the steps you must follow to build a bottom drain using a kit.

Are bottom drains necessary in a Koi pond, or can your pond be healthy without one? When is bottom drains not necessary in a Koi pond? Let’s go through this and how to install a bottom drain if your pond requires one.

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Are Bottom Drains Necessary In Koi Ponds?

Koi ponds are growing in popularity as the years go by. Koi fish are beautiful fish; introducing Koi fish into a space brings a sense of calm and tranquillity that no other animal could. They are very popular in Zen gardens, especially for this reason.

In certain cultures, Koi fish are also considered a good luck charm and represent prosperity. So, it’s no wonder these fish are becoming a staple in many gardens worldwide.

However, before introducing Koi fish and their apparent good luck into your life, you need to build a Koi pond suitable for these fish.

When you begin researching and building your pond, you might come across a bottom drain, but are bottom drains necessary in a Koi pond?

For most small garden Koi ponds that won’t have a large population of Koi fish living in them, installing a bottom drain in the pond when building it is more of a luxury option and is not necessary for the survival of the fish.

With that being said, having a bottom drain in the Koi pond reduces the maintenance needed on the pond and can help improve the pond’s water quality. So, bottom drains are unnecessary, but they can offer some nice benefits to the pond’s owner.

When are Bottom Drains Not Needed?

There are some cases where a bottom drain is not needed or recommended by professional Koi pond builders. A bottom drain is not required in your Koi pond if the following criteria are met with your Koi pond:

  • If your pond is going to be less than 4 feet deep
  • You are installing jets in your pond; these will stop waste from collecting on the bottom of your pond, which will help it stay cleaner for longer.
  • You install aerators on the bottom of your pond; this will help stop waste from settling on the bottom of your pond.

Bottom drains aren’t bad in all Koi ponds, and you can still have one installed in your pond if you want one. However, if your pond meets the requirements above, a bottom drain will not do much in the way of your Koi pond’s overall health and look.

Building A Koi Pond With A Bottom Drain

If you want to install a bottom drain into your Koi pond or your Koi pond meets the requirements of needing a bottom drain due to its size, here are some simple steps to follow to install a bottom drain.

These installation steps are for if you have bought a bottom drain kit for your pond, which is recommended as making your own will require the knowledge and experience of a professional Koi pond installer.

Step 1 – once your Koi pond has been dug out, at the lowest point in the pond, you need to install a pipe and stub it about 3 inches into the ground, and cap it off. If your bottom drain has an Air diffuser, you will need to add in an airline pipe 12 inches away from the edge of the bottom drain pipe.

Step 2 – assemble both flanges by screwing the top of the flanges into their bases. Only tighten them by hand to help prevent stripping the threads. Pressure test the flanges and cement them onto the pipes you have already installed. When you cement the flanges to the pipes, ensure the screws are aligned in a straight line; this will help you later.

Step 3 – now add cement into the hole around the pipes in the ground. You need to cover the hole until only the tops of the pipes are showing, and the cement is flat with the ground around it. 

Step 4 – when the cement has dried, remove the cement next to the bulkheads with a screwdriver. This will help make a soft transition from the cement to the rubber liner.

Step 5 – Unscrew the tops of both flanges and sweep the area clean.

Step 6 – Place the rubber liner into the pond and ensure it is aligned correctly and extends over all the pond’s edges. Cut a little hole in the rubber liner over both the flanges’ heads.

Step 7 – Place a strip of 100% silicone caulk through the holes and onto the surface of each flange around the entire flange. Gently press the rubber liner onto the flanges to stick it down.

Step 8 – Install the top of the flange again over the rubber lining. This should be easy to do if you aligned the screws earlier.

Step 9 – cut the rubber liner away from the inside of the bulkhead to create a clear opening into the pipes.

Step 10 – Install the bottom drain lid to the top of the bulkheads and connect the air defuser pipe to the drain with the elbow joint. Use some Teflon tape around the connections to ensure a tight seal. You now have a fully functioning bottom drain in your Koi pond.


Most small garden Koi ponds that will only house two or three Koi fish don’t require a bottom drain to keep the pond healthy and clean, but if you have a larger pond in your garden, then installing a bottom drain will help you immensely in the care and maintenance of your Koi pond.

Installing a bottom drain in your Koi pond is easy if you use a bottom drain kit, which is recommended if you want to install the bottom drain yourself. An alternative would be having a professional Koi pond builder install one for you. Good luck installing the bottom drain in your Koi pond!


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