How to Choose the Correct Manhole Cover

How to Choose the Correct Manhole Cover

Selecting the right manhole cover is not simply about picking a size. Four key factors determine the correct specification:

1. Load Class — How much weight will the cover bear?
2. Size — What are the internal chamber dimensions?
3. Material — Cast iron, ductile iron, or composite?
4. Frame Type — Single seal, double seal, or recessed?

Step 1: Determine the Load Class

Ask yourself: what will drive or walk over this cover?

| Situation | Recommended Class | |-----------|-------------------| | Garden / no vehicle access | AA or A15 | | Pedestrian footpath | A15 | | Car park / driveway | B125 | | Kerbside / slow traffic road | C250 | | Main road / highway | D400 | | Airport / heavy dock | E600 | | Extreme industrial | F900 |

Step 2: Measure the Chamber Opening

The cover size must match the internal chamber opening. Common standard sizes:

• 450 x 450 mm — Small service chambers
• 600 x 600 mm — Standard drainage chambers (most common)
• 750 x 750 mm — Larger inspection chambers
• 900 x 900 mm — Wide access chambers
• 600 DIA / 750 DIA / 900 DIA — Round chambers (circular covers)

Always measure the internal clear opening of the chamber, not the external frame size.

Step 3: Choose the Material

Cast Iron (Grey Iron):

• Traditional choice
• Very high compressive strength
• Cost-effective
• Suitable for most applications

Ductile Iron:

• Higher tensile strength than cast iron
• Better impact resistance
• Preferred for high-load applications (D400 and above)

Step 4: Frame Type

• Single seal frame — Standard, for most applications
• Double seal frame — Used where odour or noise containment is required
• Recessed cover — Allows tile or infill for aesthetic installations

Contact HAMS Engineering

For personalised product selection assistance, contact our technical team:

📞 +94 760 660 861 📧 info@hhkplumbing.com 📍 17/1/1, Gamini Mawatha, Mirihana, Colombo