watermain: cut in vs. pressure connection 2

[zzmarkzz]

generally, what's the difference between a cut-in and pressure connetion. is a valve vault typically required for a cut-in connection (VV is typically required for a PC). also, how do you typically call out a cut-in (simply "proposed cut-in connection")?

 

[sam74]

It's been awhile since my inspection days but I believe a cut in or "wet tap" is what I have seen. Somebody correct me if I am mistaken in any part of the description.

I believe it was a plastic or rubber tapping sleeve that was attached to the main line. It gets foggy here but I believe a short stub-out was connected to the tee with valve attached. I can't remember exactly how the tee\stub-out was attaced to the sleeve but probably a mechanical joint\gasket.

Then a tapping machine is attached water tight to the valve with a mechanical joint. The one I saw was semi manual in that its moving bit had to be physically turned into the wet pipe to make the cut. Once the pipe had been penetrated the tapping machine bit is backed to the machine and the valve is shut. It then is safe to disconnect the machine.

Then you just pour a kicker behind the wet tap like it was a normal tee. My experience was with 8 and 6 in line I think. I imagine it could be a bit different with larger pipe.

 

[sam74]

Can you describe a pressure connection for me? I am not familiar with that type of connection.

 

[RWF7437]

If you have access to a Mueller or similar Catalog, you'll find there an illustration of as so called "live tap" or "wet tap procedure. The advantage of such a tap is that it is not necessary to shutdown the existing main to make the connection. For larger lines, say 6-inch or larger, the tapping machine is operated by an electric motor. For smaller lines the machine may be manually operated.

A "cut in connection" requires shutting down the line being tapped. This is usually undesirable but sometimes necessary.

If you can't find a catalog many of AWWA's publications illustrate both procedures. For example, their Water Distribution Operator Training Handbook is an excellent source of practical information.

As to whether or not a vault is required, this is a function of how large the valve is and what type of valve it is. Consult the water system operator you are working with to find out their policy.

Good luck

 

[Maury]

Sam: What you describe with a tapping machine is pressure connection. It is done without shutting off the water or disrupting service. A cut-in requires a water main shut down, removal of a section of the main, and installing a cutting-in valve. This type of valve uses a sleeve which fits over the existing main and. It's easy to understand with a picture but difficult to describe.

 

[sam74]

Thanks for the clarification. I believe I have seen both in the field based upon your explanations but I have never heard the naming convention. It makes sense though.

 

[cvg]

A more common name for the pressure connection is a "Hot Tap" and it is generally used for a smaller valve which feeds off a larger main.

A cut in valve could be used to install an in-line shutoff valve on the main. It could also be used where a full size tee or cross needs to be installed in the mainline or where a the main / tee is very large.

If you are going to shut down the main, any type of valve or fitting could be installed.

By "valve vault" do you mean the enclosure for the valve operating stem? (Valve Box) Or an actual concrete structure for access to the valve? You will need one or the other regardless of which type valve you use.

 

[zzmarkzz]

I did mean a concrete manhole for the valve vault. We're proposing a cut-in connection since as you mentioned, it will be for a proposed 12" connection to an exsting 12" line (municipality doesn't allow same size pressure connections as cvg mentioned). Thanks for all the help.

 

[bioengr82]

The water company we consult for prefers tapping sleeves and valves whereever possible. It is usually cheaper because, as mentioned, interuption of service is not necessary. Also, because of the union contract with the water company in our area the general contractor is not allowed to 'cut in' a tee, thus unecessarly complicating the procedure. *sigh*