4 Inch Filter Brushes in Rectangular Chambers – Double Interlocked Spacing
How Many 4 Inch Brushes Do I Need for a Rectangular Chamber?
Rectangular filter chambers are one of the most common designs used in domestic and commercial pond filtration, and 4 inch (10cm) diameter Black Knight filter brushes are an excellent choice for filling them. Using a double interlocked spacing arrangement maximises the number of brushes in the chamber, increases filtration efficiency and provides a greater surface area for beneficial bacteria to colonise.
Recommended Spacing for 4 Inch Brushes in Rectangular Chambers
Double interlocked spacing means that each row of brushes is offset from the row above and below it, so that the brushes nestle into the gaps between one another rather than sitting in straight lines. This creates a much denser, more efficient filter medium than single spacing, with less wasted space and improved water contact with the brush filaments.
What is Double Interlocked Spacing?
Double interlocked spacing means that each row of brushes is offset from the row above and below it, so that the brushes nestle into the gaps between one another rather than sitting in straight lines. This creates a much denser, more efficient filter medium than single spacing, with less wasted space and improved water contact with the brush filaments.
Worked Example
A rectangular chamber measuring 24 x 12 inches (60 x 30cm) would require 32 brushes of 4 inch (10cm) diameter using double interlocked spacing to fill it effectively. The diagram above illustrates this arrangement clearly.
To calculate the number of brushes needed for your own chamber, measure the internal dimensions and use this example as a reference point. Our team can also help you calculate the correct quantity for your specific setup — just get in touch.
Tips for Rectangular Chambers
- Always measure the internal dimensions of your chamber, not the external ones
- Ensure water enters the chamber at a slow, steady rate rather than being jetted in under pressure, which can disturb settled waste
- For larger or more demanding setups, consider linking two or more chambers together
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Other Sizes
If your chamber is circular rather than rectangular, see our guide to 4 inch brushes in circular chambers. For larger rectangular chambers, you may also want to consider 6 inch brushes or 8 inch brushes as a more practical alternative.