Tag Archives: Exfiltration

All Inverts in Manholes and Lift Stations are At-Risk

The  precast concrete industry is finally focused  on supplying their customers with  preformed concrete inverts in  manholes and lift stations.

The next consideration is to begin installing  factory built thermoplastic inverts Base Liners (inverts) that  ensure  consistency of design  and  standards  for quality. Because a bottom section of the manhole with a Base Liner is complete when set in the field, it  does not require any secondary operation to complete the channels and benches; thus, preformed Base Liners also benefit underground contractors.

Lined Invert w/ channels full pipe diameter, non skid bench surface

Lined invert w/ channels full pipe diameter, non skid bench surface

The  integrity of a  sewer collection system  depends on the quality of  structures  to ensure the continued elimination of  inflow  and  infiltration (I & I).  If you analyze the anatomy of a manhole (not the most exciting endeavor),  you realize  the invert  is  critical to the continuous  flow of sewage through the entire collection system. Further, when it comes to preventing unwanted inflow, enduring watertight  pipe connections are critical.

Siverely Corroded/Eroded Invert

Severely corroded/eroded invert

If the flow channel erodes, or if  pipes  connections fail and  leak, the design integrity of the entire system  is compromised. Likewise, if the invert base and channelization is not built to  design specifications (they rarely are!), the flow design is compromised.

Over the last 25 years,  our industry has come to recognize the importance of  protecting At-Risk Concrete from microbial induced corrosion (MIC) that eats away at  concrete surfaces.

Sure Grip  CPL lift station 10' x 50' In PAby Terre Hill Concrete

Sure Grip CPL lift station 10′ x 50′ In PA
by Terre Hill Concrete

Many  utilities are specifying and installing concrete protective liners (CPL) that  protect the walls of At-Risk structures, pipe and tunnels  in their system. Over 7 million sf of AGRU Sure Grip CPL has been installed in manholes and lift stations in North America, and many millions more around the world.

Low pH – However, protecting the walls doesn’t protect the inverts from the extremely low pH wastewater that flows through  the base channels and over the benches.

Severely corroded manhole, Leesburg Fl

Severely corroded manhole, Leesburg Fl

This low pH is caused by the MIC process that develops in the pipelines and adds sulphuric acid into the wastewater. The low pH wastewater  erodes the concrete benches the same way low pH  water  in concrete swimming pools corrodes  the walls.

The Predl System

For over 25 years,  Predl Systems North America  has produced   Base Liners that replace the traditional,  built – in – place,  brick and concrete invert. Predl  has installed over 10,000 Base Liners in the U.S, and Canada;  Predl Europe has  produced over 1.5 million Base Liners of the same design that have been installed in throughout Europe.

Base Liner  top view showing full pipe size channels
Base Liner top view showing full pipe size channels

Predl Systems products offer  solutions to corrosion in manholes and lift stations by protecting the structure  from the base all the way to the street level. Predl products are  made from  polypropylene (PP),  polyethylene PE, or fiber reinforced plastic (FRP).

Predl Base Liners are custom designed to fit all  invert configurations:  regardless of changes in elevation, type of pipe, or  pipe diameters. Predl Base Liners are used in new precast, cast-in-Place,  or rehabilitation applications.

Predl  Bells are integrally cast into the concrete, they have a water-stop,  a locked-in gasket,  and a pipe stop, that combine to  ensure  lifetime protection against I & I.

Predl Bell casr in concrete

Predl Bell cast in concrete

Cut-away Predl Belllock-in gasket, water stop, pipe stop

Cut-away Predl Bell,
locked-in gasket, water stop, pipe stop

You do not need to have a lined wall to use Predl Bells; they  are used in place of rubber boots and cast-in gaskets to seal pipe  in  concrete walls . When you use Predl Bells, you do not need to use a hole former, or core  holes post production. Predl Bells provide outstanding protection against overbelling and I & I; and, they  work well in either precast, or cast-in-plece structures.

Base liner with Corprotect CPL with Prewelded Tubes

Base liner with Corprotect CPL with pre welded tubes ready to be cast into concrete

Predl PP  Corprotect AGRU Sure Grip CPL is a proven system for protecting  At- Risk concrete walls. Corprotect CPL resists ground water pressure, is highly resistant to abrasion,  and provides a long lasting, gas tight and water tight seal against  corrosion and I & I.

Predl Cone

HDPE Eccentric Cone

Predl Cones are designed to line cones (corbels) in concentric and eccentric manholes. Predl Cones can be  effectively used to rehabilitate old manhole structures.

Predl Convertible Collar seals chimney against street level I & I

Predl Convertible Collar seals chimney against street level I & I

Predl Convertible Collars complete the Predl System by sealing the chimney against inflow around the ring and covers at street level. Convertible collars can be used to rehab existing structures.

Work Together or Independently

Predl System’s family of products all work together, or they can be used independently. For example:  you can use the Base Liner without lining the walls,  you can specify the Predl Bells without the Base Liner, you can install the Convertible Collar by itself;  or, you can use the Predl Cone and Convertible Collar when rehabilitating  a manhole.

Easy Installation – Consistent Quality and Design

Predl Base Liners are supplied to precast companies complete with flow channels, benches, and  Predl Integral Bells attached; they are ready to be cast into a structure. Gone is the  need for hole-formers, coring, or  rubber flexible boots connectors; there is no need to form an invert after the base section is cast;  the  entire casting and construction process is simplified.

Large 24 x 15 x 8 Base Liner on top of core at precast plant

Large 24 x 15 x 8 Base Liner on top of core at precast plant

After the manhole with a Predl Base Liner is set in the field, the underground contractor  has no need to revisit the manhole to install an invert; and   the utility  pays for, and gets,  a professionally designed, consistent quality, corrosion resistant, watertight  invert that requires no future maintenance.