Hi all,
When installing new mains and larger (4" and greater) services, AWWA C651 is used. In my neck of the woods, it is a forgone conclusion to apply the "optional" clause C651-14 4.8.9 Backflow Protection, by installing the main up to within 6 m of the tie-in, flush using a 2" port at either end (depending on main size) of the new main; do a prelim flush, chlorinate, flush, test and then once the new main passes bacteriological testing, to open the new and existing pipes at the tie-in, swab the tie-in section and connect, then flush from the existing distribution system into the new system and call it a day.
We believe that in many cases it is better to hot tap the existing main, construct the new main beginning at this closed tapping valve, then flush from the existing main (ensuring backflow protection by the planned order of valve/blow off operation) through the new valve, pressure test against the new closed (new, resilient seat only) valve, chlorinate, flush, then to add the new main to the system, just open the connecting tapping valve, rather than opening the pipe up, swabbing and tying in. The benefits to this method are that a high-velocity preliminary flush is almost always achieved, and that the tie-in section of pipe is only opened once, during initial installation, reducing contamination potential.
There is firm resistance to this method because I do not believe it is understood, and I believe the historical basis for backflow protection instead of using a valve connected to the existing system was because of older style metal-seated valves which do not close tight like resilient seated valves do. I am aware of one City (over 1 million pop) that does do it using a connected valve, but I want to gauge the community here for feedback, since many jurisdictions only reference that C651 shall be followed, I can find nowhere that comes out and details the preferred specific methods regarding not applying the optional clause 4.8.9 except that C651 says that if the owner does not specifically include optional clauses, then they are excluded. This of course could mean that the owner just didn't bother to pay attention, or for other reasons, left it up to the operations dept or past practice or something.
So, what are some of your experiences and jurisdictions that have mandated either of these? As a side note, do you think those who enact clause 4.8.9 understand the implications, or just think that "optional"="better"?
Thanks greatly, sorry for the long-winded post!
When installing new mains and larger (4" and greater) services, AWWA C651 is used. In my neck of the woods, it is a forgone conclusion to apply the "optional" clause C651-14 4.8.9 Backflow Protection, by installing the main up to within 6 m of the tie-in, flush using a 2" port at either end (depending on main size) of the new main; do a prelim flush, chlorinate, flush, test and then once the new main passes bacteriological testing, to open the new and existing pipes at the tie-in, swab the tie-in section and connect, then flush from the existing distribution system into the new system and call it a day.
We believe that in many cases it is better to hot tap the existing main, construct the new main beginning at this closed tapping valve, then flush from the existing main (ensuring backflow protection by the planned order of valve/blow off operation) through the new valve, pressure test against the new closed (new, resilient seat only) valve, chlorinate, flush, then to add the new main to the system, just open the connecting tapping valve, rather than opening the pipe up, swabbing and tying in. The benefits to this method are that a high-velocity preliminary flush is almost always achieved, and that the tie-in section of pipe is only opened once, during initial installation, reducing contamination potential.
There is firm resistance to this method because I do not believe it is understood, and I believe the historical basis for backflow protection instead of using a valve connected to the existing system was because of older style metal-seated valves which do not close tight like resilient seated valves do. I am aware of one City (over 1 million pop) that does do it using a connected valve, but I want to gauge the community here for feedback, since many jurisdictions only reference that C651 shall be followed, I can find nowhere that comes out and details the preferred specific methods regarding not applying the optional clause 4.8.9 except that C651 says that if the owner does not specifically include optional clauses, then they are excluded. This of course could mean that the owner just didn't bother to pay attention, or for other reasons, left it up to the operations dept or past practice or something.
So, what are some of your experiences and jurisdictions that have mandated either of these? As a side note, do you think those who enact clause 4.8.9 understand the implications, or just think that "optional"="better"?
Thanks greatly, sorry for the long-winded post!
