How to Build a Koi Pond - Settlement Chambers

Get this right and half the battle is already over...

Settlement chambers are useful, albeit somewhat ugly things. Thankfully they can be easily hidden however.

Settlement chambers - essential ...

What is a settlement chamber?

Settlement chamber section

Click on the picture above for an enlargement...

We have seen that bottom drains are essential in a Koi pond. We have also seen that 110 mm piping is the way to go on bottom drains and that we don't want pumps in the water path before mechanical filtration takes place.

A settlement chamber is a smallish concrete chamber that has the 110 mm bottom drain pipes entering the bottom of the chamber vertically.

Settlement Chamber
This settlement chamber is from a pond that has 5 bottom drains, hence the 5 upflow pipes...

Pond water will flow from the bottom drains of the pond up the pipes in the direction of the red arrow as shown.

An ideal settlement chamber will be sloped from shallow to deep. The bottom drains will all face upwards and be located in the deep end of the settlement chamber, whilst at the opposite side on the shallow end of the chamber the exit pipe that feeds the primary mechanical filter stage will be located.

Being located higher than the bottom drain pipes increases the likelihood of the solids entering into the settlement chamber being collected in the deep end.

And YES, this does mean you need a waste flush valve located somewhere near the deep end of the settlement chamber so that you can flush all these nasty solids straight out and off to waste.


If the waste valve on the settlement chamber is open, the water from the pond will simply continue to pour into the chamber from the bottom drains...

Yes, it will. Unless you block these pipes off it will not be possible to empty the settlement chamber without having the bottom drain pipes filling it continually. This is an important point to keep in mind!

Now, can you see why we want the bottom drains facing upwards?

You can block these off very easily using what is called a stand pipe. This is simply a long pipe that 'stand's inside the bottom drain pipe - it needs to be a flush fit to work properly - your Koi pond builder will know how to do this. So if you have 5 bottom drains, you will need five 'stand pipes'.

With the stand pipes in place, you can empty the settlement chamber. This allows you to get rid of all the muck in the chamber quite easily as it flushes out along with the water in the chamber.

Removing the stand pipes has an interesting effect. Because the chamber is now empty, water will literally rush in from the pond through the bottom drain pipes, at a rapid rate indeed. This sudden surge of water through the bottom drain pipes has the effect of a mini flood, sucking all the solid debris in the pipe with tremendous force and depositing it into the settlement chamber from where it can be flushed to waste. Voila! Settlement chamber is cleaned, and the bottom drain pipework is also purged of excess solid waste.

Do you know how long it took me to figure all this out? When we were new to the hobby, we couldn't understand what people were talking about - stand pipes, pulling bottom drains, settlement chambers... We hope we have made it clear how things work - else please just mail or call us - we're only too happy to help.