Both unglaze and glazed vitrified clay pipes are approved and safe to use in accordance to US standard (ASTM), UK stadard (BS) and Malaysia standard (MS), thus there are no significant differences which can affect the usage.

There is no significant difference or variance when it comes to hydraulic preassure. As the sewer lines are laid, slime will build up within the internal wall of the pipes, the hydraulic flow will be no difference and there is no different values for glazed and unglazed VCP when designing sewer line hydraulic flow.

Normally, glazing are used for vitrified clay pipe which it’s clay does not meet the standard of water absorption to prevent exfiltration and infiltration. By applying glazing on the these VCP, they can safeguard against infiltration of ground water and exfiltration of effluents. Glazing also act as a cosmetic method to cover up uneven surfaces for VCP.

As for structural strength, as all galzed and unglazed VCP has gone through the local authority such as SIRIM, thus they are compliance to the strength which requires by the standard.

In conclusion, there are no significant differences or advantages between glazed and unglazed VCP. The different between ungalzed and glazed are purely because of different material (different clay) which requires different production technology to achieve the same compliance as required by the authority. Both glazed and unglazed VCP can be use safely and achieve the same structural strenth with same durable & long-lasting characteristics.