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Condron Concrete Works produce a complete range of manhole components, all of which are certified to I.S. 420: 1989 and I.S. 420: 2004 in conjunction with ISEN 1917 and supersedes I.S. 420: 1989 in October 2004

Advantages of Precast Manholes:

The main advantages of precast concrete manhole units over in situ concrete construction are:

  1. Units are factory produced to I.S. 420: 1989, I.S. 420: 2004 and I.S. EN 1917
  2. They are manufactured in wide range of sizes and depths.
  3. They are simple to assemble requiring relatively unskilled labour on site.
  4. Units are capable of being constructed as flexible watertight structures.
  5. They are supplied fitted with steps to EN 13101: 2002 Class C
  6. The structure is durable with its own inherent strength.

The diameter of our Manhole Base is 1200mm and as can be seen from Table 11, an extensive range of channel sizes and floor plans are available which would cater for the vast majority of site requirements. The all socketed units are designed so that a seal can be provided on all connections, with double spigoted sections available for connecting the outlet to the socket of the first downstream pipe. The 150mm, 225mm and 300mm channel sizes are also available with sockets and gaskets suitable for use with plastic pipes. Heights and Weights of Manhole Bases are as shown on the tables below.


Heights and weights of Chamber Rings

Table 9

Internal Diameter of Chamber Rings Wall Thickness (Approx.) Height (Approx Weight in kgs) Height (Approx Weight in kgs) Height (Approx Weight in kgs) Height (Approx Weight in kgs)
Internal Diameter of Chamber Rings Wall Thickness (Approx.) 1.00m 0.75m 0.50m 0.25m
900mm 95mm 630 - 325 205
1050mm 100mm 820 - 420 215
1200mm 110mm 1120 800 570 290
1350mm 140mm 1660 1250 850 -
1500mm 155mm 2080 1565 1050 -
1800mm 160mm 2420 - 1120 -
2100mm 155mm 3000 - 1520 -
2400mm 230mm 4700 - 2380 -

2 number 32mm diameter lifting pin for 900,1050,1200mm Manhole Chamber units/Base units

3 number 45mm diameter lifting pins for 1350,1500,1800mm Manhole Chamber units.

3 number 50mm diameter lifting pins for 2100,2400mm Manhole Chamber units.

Heights and weights of Manhole Bases

Table 10

Channel Size Overall height (Approx.) Effective Height (Invert to top of Base) Approx Weight in kgs for Base Types Approx Weight in kgs for Base Types Approx Weight in kgs for Base Types Approx Weight in kgs for Base Types
Channel Size Overall height (Approx.) Effective Height (Invert to top of Base) Type 1 Type 2 Type 3 Type 4
150mm 750mm 600mm 1960 - - 1800
225mm 750mm 600mm 2120 - - 1850
300mm 750mm 600mm 2120 2000 2050 -
375mm 750mm 600mm 2120 2000 2050 -



Table 11

Plan Type 1 2 3 4
150mm Diameter Channel
225mm Diameter Channel
300mm Diameter Channel
375mm Diameter Channel

Manhole Base with 300mm ø channel (Type 1) showing correct position of Butyl Sealant

manhole base

All chamber sections are fitted during manufacture with 350mm wide plastic coated aluminium rung steps, which are spaced 250mm apart, thereby providing a uniform step interval in all units.

The black polyethylene covering on the steps is resistant to nearly all media and also prevents sparking when walked on with iron-mounted boots. The steps comply to EN 13101: 2002 Class C

Chamber Rings can be supplied reinforced if required. All sections are jointed using our CS 202 Butyl Sealant giving an immediate and flexible watertight joint.
Heights of chamber sections are as shown on the table.

Permissible angles under I.S.6: as follows Table 6
Nominal Size mm Permissible Angle
150 90°, 45°, 22½°
225 90°, 45°
300/600 45°

NOTE: All chamber sections are to be stored vertically on site to prevent rolling.

The cover slabs, which are all reinforced, have a different thickness for different diameters. All are provided with a 600mm (min) diameter opes and a socketed base which allows a butyl sealant joint to the top chamber section.

Cover Slab Dia. Overall Approx. Thickness Effective Approx. Thickness Approx. Weight (kg)
900mm 230mm 170mm 340
1050mm 230mm 160mm 480
1200mm 230mm 150mm 580
1350mm 300mm 200mm 1020
1500mm 300mm 200mm 1260
1800mm 300mm 200mm 1780
2100mm 350mm 230mm 3200
2400mm 380mm 250mm 4140

I.S. 420: 1989, I.S. 420: 2004 and ISEN 1917 incorporates routine water absorption tests, works proof load tests, maximum load tests, cube crushing tests, cover to reinforcement, complete manhole hydrostatic test and installed step tests. Our Quality Control Team carries these tests out daily to ensure compliance to the relevant standards.


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