Concrete Pipe Sanitary Sewers - To Clean or Not to Clean?

[MarshfieldTimC]

Our City has many sanitary sewers consisting of concrete pipes. This pipe material was commonly installed between approximately 1950 and 1970. As these concrete pipes age, hydrogen sulfide attacks the wall surface and deteriorates the pipe from the inside, mostly above the water line.
My question deals with maintenance of these older, deteriorating concrete pipes. Cleaning using a jetter (typically with a full-circle spray nozzle) is frequently warranted to remove grease and debris. Should we be jetting/cleaning these pipes? Does jetting/cleaning remove the deteriorated surface exposing the underlying concrete and accelerating the deterioration process; or does cleaning remove the acidic slime thereby slowing down the deterioration process?
So, in the interest of extending the life of a concrete pipe sanitary sewer, should we clean more frequently, less frequently or only when absolutely necessary?

 

[bimr]

One would think that the pressure of the water pumped through the spray nozzle is adjusted so that the water pressure will not damage sound pipe. Cleaning is also necessary so that the condition of the pipe can be assessed.

During the cleaning, deteriorated pieces of pipe are removed by the spray nozzle exposing fresh surfaces to the corrosive actions of the wastewater. Sulfide reducing bacteria and gases are also removed during cleaning. Probably a wash.

Too frequesnt cleaning will probably damage the concrete pipe, but who has money for that.

 

[cvg]

would you rather pay for sewer backups and flooding or keep cleaning and replace a pipe sooner that will need to be replaced soon anyway?

 

[nackra]

clean and rehab the sewers with a "liner"
Inliner and Insituform are a couple of options

 

[jgailla]

+1 for a liner, if you can find the money. In general it will be worth it in the long haul. It's possible to get another 20 years or more if the concrete pipe isn't too far gone already.
If you can't get the money, cvg is spot on as usual. I would think that the increased rate of deterioration due to jetting would be very small in comparison to the sulfide attack on the concrete pipes.
I haven't studied it, but I think that the grease and debris is not protecting the concrete from attack or enhancing the deterioration in any measurable sense.

 

[cvg]

get a video inspection before and after and make a real evaluation

 

[dicksewerrat]

Lining a pipe will give you somewhere between 40 and 60 years of service. Lined pipes are also easier to clean . You can go 4-6 years between cleaning if little grease buildup in the past. They can line almost any size and shape of pipe.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com