Minimum Velocity in Potable water pipe
Minimum Velocity in Potable water pipe
(OP)
I am working on a design for a replacement pipe line for potable water. I am looking for a published standard or guidline that states what the minimum velocity in a potable water pipe should be. Thank you.





RE: Minimum Velocity in Potable water pipe
Maximum velocities are much more critical and are governed by considerations of economics, water hammer, energy costs, etc.
good luck
RE: Minimum Velocity in Potable water pipe
A generally accepted minimum velocity for maintaining pipelines free of small sand particules and other debris would be around 2.5 to 3 ft/sec.
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RE: Minimum Velocity in Potable water pipe
RE: Minimum Velocity in Potable water pipe
RE: Minimum Velocity in Potable water pipe
However the distribution system shall be designed to maintain treated water quality. Systems shall be designed to maximize turnover and to minimize system residence times.
Reference: Recommended Standards for Water Works.
RE: Minimum Velocity in Potable water pipe
RE: Minimum Velocity in Potable water pipe
RE: Minimum Velocity in Potable water pipe
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RE: Minimum Velocity in Potable water pipe
RE: Minimum Velocity in Potable water pipe
RE: Minimum Velocity in Potable water pipe
Are you saying that was the wrong question?
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RE: Minimum Velocity in Potable water pipe
are returned to service." There are I suspect many other references having to do with what is otherwise involved with maintaining water quality (and avoiding stagnation etc.) in water systems, including e.g. publications of EPA and AWWA(RF) etc.
RE: Minimum Velocity in Potable water pipe
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RE: Minimum Velocity in Potable water pipe
However, the design of a water main should not be based on a minimum velocity under normal conditions. The size of a water main should be dictated by the available flows and pressures under peak demands. (Fire flows if fire protection is provided)
If the goal of the question is to determine the appropriate velocity to clean the main, then 2.5 ft/s should suffice. If you are trying to determine the appropriate size for the main, minimum velocity is not the parameter you should be considering.
RE: Minimum Velocity in Potable water pipe
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RE: Minimum Velocity in Potable water pipe
Here is an excellent book William S. Jenna "Design of Fluid Thermal Systems 2nd Ed." It also has a table of fluids listing the Economic Velocity Range, for some common fluids. I highly recommend this book, I have had it since 2002 and it constantly impresses.
Anyhow for water it lists a range from 4.4 ft/s to 8.8 ft/s. Personally depending on the actual size used I don't see a problem going down to around 3.5 fps, but would avoid any lower.
P.S. be sure that the size you specify isn't a odd ball size, (like 5", or 1.75"). Pipe and fittings can be found, but is a pain in the butt for Contractors to find and they will curse your name.
RE: Minimum Velocity in Potable water pipe
For petro lines the first approximation for defining a diameter selection range is based on min velocity of 3 ft to max 10 ft/sec.
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RE: Minimum Velocity in Potable water pipe
The reason I mentioned the min. was not in relation to optimizing the pipe OD, but because that is what the originator asked about, -the minimum velocity.
RE: Minimum Velocity in Potable water pipe
I think its good that somebody's trying to relate an answer to the original question.
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RE: Minimum Velocity in Potable water pipe
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RE: Minimum Velocity in Potable water pipe
RE: Minimum Velocity in Potable water pipe
Is there a semantics issue here. i noticed the chemical tag to your handle. I'm going to assume that you're not in charge of designing a municipal water system, but maybe something more like the connection of a building or a couple of buildings to an existing system?
in the latter:
we have a 3/4" to 2" domestic water line connecting our most of our buildings to the system, The main design factors are:
1 keeping the velocity near or above the flushing velocity to prevent sediment buildup (make the pipe smaller) at peak flow
2 keeping Head Loss to fixtures and line friction to an acceptable level (make the pipe bigger) at peak flow
3 cost of materials (make the pipe smaller)
Sprinkler lines to buildings get their own bigger line off the system since the pipe size will have to be greater for greater flows. You wouldn't want to just have one big line serving domestic water and fire water though because of that min. velocity issue.
RE: Minimum Velocity in Potable water pipe
With modern subdivision layouts, some have dead end streets that do not have a ROW to connect the respective dead ends. In this case I use a 50 mm PE pipe for up to 10 services, instead of the minimum 100 mm reticulation pipe. Dead ends are always a problem due to the build up of sediment (& consumer complaints), & the same result occurs (distribution of any sediment slowly & constantly, into ALL services), rather than using flushing points at the ends of dead ends.
Fire flows are still confined to hydrants located only in 100 mm pipes, with the furthest house (from a hydrant) only 5 services distant.
If the dead end street is fairly long, a 100 mm pipe is laid until there is only 10 services left, then a 50 mm PE is used.
Since this practice was developed, the number of dirty water customer complaints (in these areas) has dropped significantly.
RE: Minimum Velocity in Potable water pipe
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