| Catchbasins, Manholes
& In-line Inlet Drain Application Notes
& Installation Guidelines
As noted in the CPP manual entitled "CORROSION
RESISTANT GRAVITY DRAIN PIPES and CULVERTS" (page 11), precautions
should be taken at connection points as these have historically been
a problem for all buried pipe systems, no matter the pipe's raw material
base. This is especially true for connections at CATCH BASINS, MANHOLES,
DRAIN BASINS, INLET DRAINS and in
the union joints of such catchments requiring risers .
At the surface, if traffic is expected, or at great depths where soil
drag-down can occur from the soil locking into riser corrugations,
or where water tight joints are required, poured concrete around all
of the connection joint and part of the fitting should be employed.
In constructing FIELD FABRICATED CATCH BASINS and MANHOLES,
contractors can easily employ CPP fabricated or machine molded fittings.
However, in these FIELD CREATED systems, fittings or the pipes used
as risers, may be oriented in a manner for which the part was not originally
designed or intended. While backfill around such structures are nearly
the same as that for pipe, extra procedures should be considered in
- Where H-20 or greater traffic is expected, at least
concrete should be used under metal grate lids, and around the
lip of the plastic part holding the metal grate.
- Where grassy swales or paved swales intersect H-20 traffic bearing
catch basin grates and offer a potential moisture change in compacted
soils, 6" of concrete or an expanded 95% compacted backfill
zone of dimension determined by an engineer should be used.
- CPP fabricated and machined Tee's are often used to create catch
basins, and manholes. The products were originally designed to be
horizontally installed in a pipeline, not installed in a vertical
manner that would put unexpected stresses on the part wall. In such
field-fabricated systems where traffic is expected, 6" of concrete
should be used both at the surface and around the fittings to the
haunch line of the fitting.
- CPP pipes make excellent risers in
dams and drop manholes. The vertical placement of corrugated pipes
does invite a soil drag-down stress on the pipe as the soil interlocks
into the corrugations. Surface traffic or the continuous water flow
in a dam riser will produce additional downward stress on the manhole-catch
basin tee joint at the bottom of such systems. To deflect this downward
stress, 6" of concrete is recommended around the inlet top,
and at the bottom around the fitting to the haunches.
- CPP fittings
used in water-resistant RISER PIPE applications should be completely
encased with poured concrete. In these applications, the fitting
acts as a concrete form for the system being constructed because
their use saves more money in field fabrication labor expense than
the cost of the plastic part being substituted for the concrete
Crumpler Plastic Pipe, Inc.
Post Office Box 2068 / Highway 24 West
Roseboro, NC 28382
TEL: 1-800-334-5071 · 910-525-4046
FAX: 1-800-CPP-PIPE ·
General Information, Sales, & Support: firstname.lastname@example.org
Engineered Sales: email@example.com