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Ask Don!
USABlueBook
Technical Training Manager |
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Mainline Flushing
(or, Remember to Flush) |
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| By now, things are getting busy with construction, but let’s not neglect the pipes we already have in the ground. We must flush to remove impurities, control corrosion, and maintain chlorine residuals. |
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| There are six parts of a flushing program: |
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- Public Notification. This communication will not eliminate, but will greatly reduce complaints of colored water.
- Flushing from the Source Outward. Done in segments, this saves time by decreasing overlap in areas flushed and improving flushing efficiency.
- Flow Velocities. To achieve the desired 5 feet per second, flow must be unidirectional, which means flow comes from only one direction. To do this, you will need to shut valves. The easiest way of calculating velocity is using the graph shown at right.
- Safety. Address personnel and public health by properly controlling traffic to prevent injury, and by maintaining a system pressure above 20 psi to prevent pathogen entry into your system. Remember to open and close valves slowly to prevent system damage.
- Establish Objectives. Apply measurable goals such as turbidity reduction or chlorine residual standards in the flushing process.
- Document Results. Developing a plan always works best when you can look back and learn from the past.
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| For more information, please contact Don at 503-544-0456 or dvanveldhuizen@usabluebook.com, or LoAnn Mayer at 847-377-5162 or lmayer@usabluebook.com. |
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| Calculating Approximate Velocity of Flow in Pipe |
| This diagram is based on flow in new pipe with diameters being equal to the nominal size. |
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| Example: A 6” pipe is flowing full at 400 gpm. Draw a line through 400 and 6 to intersect the Velocity line at about 4.5. |
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