Combination Air Vac Valve (CAV) Relocation
Combination Air Vac Valve (CAV) Relocation
(OP)
Due to a potential conflict with a another utility provider I have to relocate an existing CAV and the vault. The CAV is at high point of a 16" ductile Iron water transmission pipeline. Can I relocate the CAV by installating a 16" "Tee" at the high point and then extending the branch of the tee horizontally for about 20' upto the proposed CAV location. Anyone has any prior experience with this type of an issue. Like to hear your experience.
Thanks.
Thanks.





RE: Combination Air Vac Valve (CAV) Relocation
You also run a risk of stagnant water in the dead leg created by remotely locating the combinatin air release valve. This stagnant water may be pulled back into the transmission main with vacuum.
Is it possible to eliminate the valve?
Have you considered moving the valve downstream? The air will be pushed down stream by the fluid. It may be acceptable if you install the valve at the location where the transmission line starts to slope downward.
RE: Combination Air Vac Valve (CAV) Relocation
20' is not a long displacement. Take a look to the pipeline gradient line and check whether it's a critical point or not (too close to gradient line, risk of major negative pressures). You should also try to re-place the valve so that it is being heat by the negative surge sooner than the main pipe.
Anyhow, If you provide a suitable slope toward your new location (let's say minimum 2.5% to be on the safe side) and try to get the connecting pipe with a diameter as close to the main pipe as possible, then it should be fine.
Please note the function during the negative pressure is more important. Under normal pressure, the trapped air would go forward to you detour branch and thus out of the main pipe.
RE: Combination Air Vac Valve (CAV) Relocation
The air release is probably more important unless the vacuum release is installed to protect the pipe. Sometimes thin walled pipes are installed that can not withstand the maximum vacuum created by the water as it drops in elevation. Probably not a good design practice if that is the case.
Not that the outlet of the air release needs to be above grade and out of the vault.
RE: Combination Air Vac Valve (CAV) Relocation
RE: Combination Air Vac Valve (CAV) Relocation
RE: Combination Air Vac Valve (CAV) Relocation