I got into the department just as we were switching from 3 to 4 inch. First off, DC uses 3 inch, so i'm sure with most big cities the departments around them sort of emulate them (since they were around first and all).
If you lay dual 3 inch lines from the hydrant, the friction loss difference is not that much different than a singe 4 inch line.
You can move a 3 inch line that is filled with water much easier than 4 inch.
You can drive over 3 inch and 4 inch you cannot.
Thats just what i know, and is surely not all there is to it. Plus people are more apt to lay out as a precaution since its so easy to re rack 3 inch.
If you lay dual 3 inch lines from the hydrant, the friction loss difference is not that much different than a singe 4 inch line.
You can move a 3 inch line that is filled with water much easier than 4 inch.
You can drive over 3 inch and 4 inch you cannot.
Thats just what i know, and is surely not all there is to it. Plus people are more apt to lay out as a precaution since its so easy to re rack 3 inch.
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