13 May
If you are getting ready to install a septic tank or a new drainage run you will need to be able to get your levels right here is how you do it:
First find out what fall you will need on the drains:
- Minimum gradient for surface water drainage = 1:100
- Minimum gradient for foul water drainage = 1:40 (1:80 if wc connected)
Calculating
Fall = Distance ÷ Ratio
If a drain length is 20m and the ratio is 1:40
Example
20,000mm ÷ 40 = 500mm
Simple!
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