Water Main Valve placement question.

[kdiehl]

I am taking the level 3 Operator cert test tomorrow and these practices tests are driving me nuts. I did my homework and studied very hard but I keep running into conflicting questions.
The Question is the same in two editions of the AWWA Operator Certification Study Guide.
One is the 5th Edition, the other is the 6th Edition(newest).
Each one has a different answer for the same question and cites a different reference so which is right ?
I realize in the real world the difference between the tow answers is pretty trivial but for testing purposes which one will be right ?

The question:
Water Mains that are 12 inches or less in diameter should have isolation Valves that are located not more than _____ft between each other.

It is word for word in both editions however The 5th Edition cites 800ft as the correct answer using the 2nd edition of the AWWA Water Dist handbook.
The 6th Edition study guide cites 1000ft as the correct answer using the University of Sacramento Water Distribution Training manual. That one I have and 1,000 ft is what it states but for testing purposes which one is right ???? How can two books put out by the same source have two different answers ?
If anyone has the newest edition of AWWA Water Transmission and Distribution (5th ed I think ??) can you post what it says ? I have found alot of inaccuracies in the University of Sacramento book but the edition of AWWA Trans and dist I have is 2nd ed and only states Valves placed at intervals.
Thanks.

 

[cvg]

depends on the source and on the circumstance, but I would probably not rely on something published by a university.

for instance, the 10-states standard which is widely adopted says

Valves should be located at not more than 500 foot intervals in commercial districts and at not more than one block or 800 foot intervals in other districts. Where systems serve widely scattered customers and where future development is not expected, the valve spacing should not exceed one mile.

 

[kdiehl]

ok Thanks. I have to agree with you about the Sacramento book. I ordered that course first and got half way through it and did not like the way it was laid out. I found the AWWA Books to be much better. I only regret not buying a newer edition of the water Transmission and Distribution but I could not afford it. I bought an older second hand edition. It just bothers me that the newer latest edition Operator Certification Study Guide calls for 1,000 ft based on the Sacramento book. The Operator Study Guide is published by the AWWA and ABC. I'm gonna go with 800 and if I get it wrong so be it. I don't think 1 question is going to pass/fail me but I would still like the right answer. I mean the reason why we educate ourselves is to have knowledge, not just get by a test right ?

 

[bimr]

As cvg points out, there is no correct answer to that question. The Ten States Standards is a recommendation just like the AWWA standards unless the standard is formally adopted by the particular municipality. Note the Ten States say "should" and not "shall".

 

[coloeng]

Per AWWA Water Transmission and Distribution, 4th Edition:

"Shutoff valves should be provided so that areas within the system can be isolated for repair or maintenance. In order to minimize service interruptions, valves should be located at regular intervals and at all branches from the arterial mains. Where mains intersect in a grid, at least two (preferably three) of the branch lines should be provided with valves. The distribution system should be planned so that most of the flow is maintained even if any section of the system is taken out of service."

No specifics on distance between valves. As with anything, testing isn't always based on real world situations.

Hope this helps.

 

[rconner]

Good comments all. While I don't know much about answers to really over-simplified test questions, I do know nearby valves that are working to keep water off certain locales are quite helpful to utilities when they need them.

In fairness to the developers and maintainers of same however, the above partial passage first quoted from the Ten States water standard actually left off the really more encompassing opening statement/actual "requirement" from Sec. "8.3 Valves" of that particular 10 States section that reads as follows:

"A sufficient number of valves shall be provided on water mains to minimize inconvenience and sanitary hazards during repairs..." [It then provides the general ("should") spacing etc. guidance listed above.]

This requirement or is interpreted differently in different locales, and I guess a rather well-rounded education with regard to details may best be had by perusing many different specifications. In closely looped distribution mains and/or or complex multi-pipe systems, with multiple cross-connections and various critical crossings etc., much more Engineering consideration is needed, and often more valves.

With a multitude of valves in some systems, it further follows that knowing exactly where they are, exactly how they open and close, and also whether they are now open or closed at any particularl time, is equally important to most efficient operation of systems.

Hope you passed your exam.

 

[kdiehl]

Thanks for the replies. I won't have my results for a few more weeks. The test was nothing like the practice tests or study materials.

 

[itsmoked]

Well hopefully, unlike when I took my test, when you returned to your car, it still had its radio and all your belongings still in it. LOL

Keith Cress
kcress -

http://www.flaminsystems.com