Settling Chambers

What is a Settling Chamber?

Many new hobbyists have a bit of trouble understanding the settling chamber without actually seeing one in action.  Basically a settling chamber (often referred to as an SC) is like a skimmer, except instead of water flowing from the top of the koi pond, it flows from the bottom.  An SC is purely a mechanical filter designed to remove solids before the water is sent to the biological filter.  The reason for this is the bio filter will be far more effective if it doesn't have to deal with all the solid waste. 

The SC is placed near the koi pond and is an in ground container or tank of some shape.  Most will be a cone or cylinder shape and use a vortex motion to aid in the settling.  Water flows from the bottom of the koi pond, through a bottom drain, into the SC.  The solid waste from the koi pond flows gently into the SC and settles at the bottom of the tank.  A pump then pulls the cleaner water from the top of the SC and sends it to the bio filter.  Usually a valve is placed at the bottom of the SC so you can simply open in and drain away the settled waste.  However some settling chambers are buried flush with the ground and instead of a valve, a sump pump, or solids handling pump is used to clean out the SC.

The design of the SC can take many shapes.  The most effective is the cone shape.  This design has the water entering in at an angle so the water can spin in the tank.  This increases the settling effect.  But a cone shape is not required.  Some settling chambers can take the form of a second smaller pond connected by the underground pipe.  When digging your own pond style settling chamber, be sure to make it deep and as close to a cone shape as possible to increase efficiency.  This second pond can also be filled with floating plants that will help consume the koi waste creating additional filtration.  However this second "settling pond" will need to be cleaned frequently since it is removing the majority of the solids from the larger koi pond.  So keep this in mind when designing it.

One thing to keep in mind with a settling chamber is flow rate.  If the water flows through the SC too quickly, then the waste from the koi pond will not have time to settle out and it will simply pass right though the pump.  The efficiency of the SC is all about dwell time.  The longer the water dwells in the tank, the better the settling.  As a general rule the SC needs to be 10% of the flow rate.  So  if you have a 4000 GPH pump, then your SC needs to be at least 400 gallons.  That's a pretty big tank!  Many times, on larger koi ponds, all of the water does not flow through a single SC.  Instead several lines are created, each with their own pump.  For example the bottom drain flows into a smaller SC and a smaller pump sends it to a filter.  Then a separate pump is used in the skimmer and sends it to another filter.  Having separate feeds like this allows you to use smaller pumps and smaller sized equipment, and when you add up the flow of all the pumps, you have enough circulation for the size of the koi pond.

Another way to get around the giant settling chamber and still be effective is to use a Microscreen.  There are several versions of the microscreen on the market today.  Basically the water passes through a fine stainless steel mesh, usually 250 or 500 microns.  The screen will quickly clog so various self cleaning systems have been developed.  The most popular is the spray bar.  The screen is designed like a round drum.  (imagine a 5 gallon bucket and the walls of the bucket are the mesh.  Water is pulled through a pipe in the middle of the drum.  The pipe comes up through the bottom center of the drum and it spins on this pipe.  Water after the pump is sent back to the center of the drum through small spray bars that constantly turn and spray the mesh clean.  Using a self cleaning microscreen such as this can greatly increase the efficiency of a settling chamber.  You can send much higher volumes of water through a smaller tank and the microscreen will prevent debris from passing through to the pump and filter. 

More Settling Chambers

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