Min. Slope for a Water Main?
Min. Slope for a Water Main?
(OP)
Hi Eng's,
anyone ever heard about a min. slope for a water main?
anyone ever heard about a min. slope for a water main?
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Min. Slope for a Water Main?
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RE: Min. Slope for a Water Main?
Thanks,
BD23
RE: Min. Slope for a Water Main?
RE: Min. Slope for a Water Main?
Clifford H Laubstein
FL Registered PE 58662
RE: Min. Slope for a Water Main?
My 2 cents,
Carl
RE: Min. Slope for a Water Main?
If you have slopes in a potable water system you will end up looking like a sewage system with pump stations every so often else your carriers will strike magma.
A water filtration plant is whats required here or the authority will have to embark on routine maintanence and flush their system even using pigs if required.
RE: Min. Slope for a Water Main?
For pharmaceutical (water) application we maintain 1 inch in 10 feet slope in the direction of water flow. This is as per the recommendation of International Society of Pharmaceutical Engineering (ISPE). Perhaps this gives good drainability.
Regards,
RE: Min. Slope for a Water Main?
If it's surface water pre-treatment then there may be some solids etc, but if your collection point is OK then this will be minor and provision of scour points and relief valves is enough.
There are minimum velocity rules to avoid deposition of solids in sewers - 0.7m/sec is a number used in pressure mains. Note that most sewers and water pipes have periods of low-flow and static periods.
Gibfrog has a good point re. preserving a disinfectant residual if it's a treated water main.
And for $64K, the leading question is 'What sort of settlement and encrustation problems have you had before?'
AndyLe
RE: Min. Slope for a Water Main?
Yes, there is a criteria for min. slopes in water supply, espacially for transmission mains(under Pressure).
The idea is to facilitate entraped air to be released from air valves and to drain the pipe at washouts, if necessary.
Normally, 1:250 against the flow direction and 1:500 with the flow direction. But, you have to consider other services like sewerage.
If you need referance, please contact hansid@emirates.net.ae.
Regars
Hansid
RE: Min. Slope for a Water Main?
RE: Min. Slope for a Water Main?
RE: Min. Slope for a Water Main?
Just my thoughts...
BobPE
RE: Min. Slope for a Water Main?
KRS Services
www.krs-services.com
RE: Min. Slope for a Water Main?
RE: Min. Slope for a Water Main?
I agree with you that the municipality's request or suggestion is utter nonsense, but alas, they are the client. For those whom are not too familiar with the municipal structure, the Directors, Superintendents and other managers are in a position of supreme power and have the legislative ability to request just about anything they wish. It boils down to politics and ideals.
The municipal official believes that a minimum slope for watermains are required, no big deal. Have the municipality provide examples of where he/she has seen slopes work and proceed accordingly. Like I mentioned previously, I provide some slopes too, but I was in a northern environment and utilized them to evacuate air and to drain some mains in the winter (park closures). Never for the buildup of fines settlement.
KRS Services
www.krs-services.com
RE: Min. Slope for a Water Main?
For treated water you should be removing the suspended sediment before it goes into distribution and not carry it through to the consumer. If the main operates at variable flow then the solution is to flush it periodically.
For trunk mains I use a minimum slope of 1 in 500 towards an air valve and 1 in 300 away from an air valve.
For distribution pipes adequate air relief is provided through hydrants and consumer connections and, as stated by BobPE, it is not worth trying to maintain a minimum slope.
For steep slopes a concern can be high velocities during initial filling.
Brian
RE: Min. Slope for a Water Main?
RE: Min. Slope for a Water Main?
RE: Min. Slope for a Water Main?
Whatever slope you have will do nothing in the face of the water pressure.
Slope only matters for gravity pipes.
RE: Min. Slope for a Water Main?
We are discussing transmission pipelines ONLY.
Please understand the design, construction and maintenance.
In design, the engineer must consider the construction and operation side also.
My experience in Pakistan and UAE suggest that by providing a minimum slopes against and with flow, the operation and maintence becomes much safer. Otherwise, the designer must preapre an operation manual with details of valve operation schedules/nr of turns to be open/close in specfic duration. The designer must produce calcuation for airvalve sizing,filling and emptying process. Check negative pressure.
By having defined low point (washouts), it will be much safer to darin the pipeline to carry out the emergency work.
Similarly, having defined high points (airvalves), it will be quick and safe to bring the pipeline in operation. Otherwise, it will take hours and might force section by section filling.
The minimum slopes are very useful when the water transmission systen is having working pressure 24 bars and having high velocity.
The design is always done with assuptions and the assuptions are modifed based on the degree of relibility.
The minimum slopes must also take care of other utilities.
RE: Min. Slope for a Water Main?
I think we have established that trunk mains should have a minimum slope, to and from air valves, to aid air evacuation. But this is not necessary on distribution pipelines where air is easily evacuated through hydrants and connections.
For main transmission pipelines the rate of filling and air valve sizing need to be selected to avoid high velocities under air pockets and air valve slam causing transients. This is usually of less concern with high pressure pipelines because the pipes are not pressurised to their design pressure until after they are filled.
Also with steep pipes it may be necessary to limit the filling rate to avoid high velocity free surface flow and possible cavitation damage to the cement mortar lining.
Brian