Wastewater bypass, Contractor wants to use fitting to bypass a MH the are replacing, Thoughts? 1

[StuartMurray]

Situation: 15"PVC line with peak flow estimated at 4500gpm, contractor proposes using 45degree PVC bends to bypass MH they are replacing. They plan to set up a standard "pump around" bypass for 24hrs to allow high early strength concrete to cure. Replace MH, vacuum test, and coat; then reset "pump around" to accommodate MH tie in. The benefits are that they work at night and avoid multiple days of pumping peak discharge; regardless, the pump around will be sized to handle estimated flow with a second pump and discharge piping as a backup.

 

[AgMechEngr]

If they are suggesting a "pump around" via gravity with 45 degree bends to bypass the manhole, I would not approve. You have substantial flow and would be in major trouble with an obstruction at the bends. The public utility will likely have objections to direction changes between manholes as well. Be safe, do what is standard procedure, and pay for the time needed for a proper pump around.

 

[bimr]

A 15-Inch gravity pipe will not flow at 4,500 gpm. Would you restate your scenario? It is not clear what you are trying to do. This seems like a common scenario in sewer maintenance.