Manhole vs. Junction Box

[OkiGIS]

I am currently involved in doing a GPS survey of a potable water distribution system. We are using spatial data standards to define the points we collect. The point "Water Junction Point" has three subtypes: manhole, junction box, and valve pit. I was hoping someone could more clearly define the differences between those three subtypes for me.

Thanks,
WP

 

[cvg]

i think terminology is highly specific to the particular region of the world you are in, so it might help to specify where you are.

However, in this region (southwest US) - we really don't use any of those terms exactly...

manholes are rarely used for water systems here, however sometimes a vault will be constructed allowing entry to operate a large valve. it would be large enough to allow maintenance and replacement of the valve if necessary. However, typically most valves here are direct bury and have no manhole. They usually have a "box" which is really a pipe or split sleeve which allows an operatior to access the valve operating nut from the surface. This might be similar to your "valve pit".

By "junction" i assume you mean a tee or cross where two waterlines connect. Typically there is no way to determine the location of this junction in the field and would be no junction box. Perhaps you mean a service connection / meter box where a building water service line connects to the main. We usually have a small box near the edge of the road which contains a meter and a corporation stop.

 

[LHA]

I have some experience with the SDS System. The biggest thing that characterises it and its close sibling, the AEC CADD standard, is that they both use FAR too many subcatagories for labels. Consequently, I use only a very small fraction...one doesn't normally need Mains and Laterals and Fittings and Fire lines and Abandoned Mains and Markers and Junctions - each with subacatagoies - all on different layers.

First, make sure you need all three you have cited.

It seems as if the labels are to serve any logical purpose, it is to exclude the other structures. Using that, I would label an underground stucture with valves and meters in them as "valve pit"; any with more than two penetrations as "junction box"; and any with change of direction only - without junctions, valves and meters - in them as "manhole". However, using that rational, I can't recall ever seeing a water "manhole", for the reasons given by cvg.

Remember, amateurs built the ark...professionals built the Titanic. -Steve

 

[gtrainor]

Manholes are used often for large valves and/or a series of valves, or for large metering and pumps. But I refer them as vaults (manholes for water systems) that allow whole body entry. Google water-vaults, meter-vaults...As mentioned in another thread, manholes are defined as a structure large enough to allow a human reasonable access. I would stick to the reasoning CVG has said.

 

[skillz]

For water main projects that I've designed I use both valve vaults and junction boxes.

Valve vaults - round structures similar to manholes that allow access to a valve. The structure has openings for the water main to enter/exit the vault which are usually booted and then brick/mortared to prevent water from filling up the vault. I design 4' diameter valve vaults for water main 8" and less, and 5' diameter valve vaults for water main 10" and greater.

Junction Boxes - used whenever you need more room to access something than a valve vault will provide. They are precast concrete box structures, custom made to the size specified on the plans. The size depends on how much room you need. I had a box that was probably 10' x 6' used for two butterfly valves and a meter stationed between townships so that they could measure water usage in an emergency where the other town would need to be given water.

I usually never design valve boxes to be placed on top of mainline water main valves because a lot of public works depts. like to be able to access them in case repairs are necessary. Vaults can typically be $3000-$4000 each, so cost could be an issue regarding whether or not to use them.