Temporary Bypass Water

[bsmarks]

I am currently working on a project where we are replacing an existing water system in a neighborhood. Most of the area is residential but there are some commercial and industrial buildings. The area is being divided into phases to minimize the duration where temporary water is being provided. I'm trying to find out if there is a guide on sizing the temporary pipe. The locality that this work is being done for doesn't have any guides for temporary water bypass. Any suggestion would be very much appreciated.

 

[bimr]

I have never seen a guide for temporary water services. Typically it is specified that the contractor is required to maintain water service during construction. It is also typically specified that the contractor develop a plan to do this and submit the plan to the engineer for approval.

Having said that and not knowing the size of your system, the minimum size of water main for modern water distributions systems is 8-Inch. The 8-Inch water main will handle the typical residential fire flow requirement.

 

[semo]

On a lot of past projects where we've replaced mains no temporary was installed.

Instead the new mains were installed for the area (sometimes a complete community) connected to the distribution system, and tested. This meant that at some point there were two live distribution systems. The only shutoffs were done at the point of connections and for a short time period.

Once the new system is hot and bacteria free, service connections can be transferred over. After all the service taps and connections are made, the old main was cut off. This usually involved an isolated or short time shutoff as well.

Note that you will probably find some service taps that you didn't know about so they need to be ready to make additional taps once the old mains are abandoned.

 

[bsmarks]

Thank you for the answers. Unfortunately having two systems running at the same time is not possible. This is being done in relatively narrow streets and there are a lot of other utilities in the road.

I am under the impression that using an 8-inch line for temporary is not what is typically done. I've mostly seen 2 and 4-inch lines for temporary.

Seems odd that there is no guideline. I know that standard pipe flow and pressure designs are not applicable to temp lines but there must be some minimum.

 

[77JQX]

Are you trying to maintain fire service throught the temporary pipes? If so, then you'll want a minimum of 8-inch diameter. If you're not trying to maintain fire service, and the system is metered for consumption, then the billing history could be used to get a feel for the demands that will need to be satisfied. You'll want to apply a peaking factor to the billed usage to account for diurnal and coincident demand factors.