What is the minimum thickness for a GRP bathtub according to IS 6411?

The laminate shall have a minimum thickness of 3.0 mm (Clause 4.3).

What is the maximum permissible water absorption for the material?

The maximum water absorption shall not exceed 0.20 percent by mass, as specified in Table 2.

How is the surface quality and cure of the gel-coat checked?

The Barcol hardness of the gel-coated surface should be a minimum of 40 (Table 2).

Are there standard sizes for these bathtubs?

Yes, Table 1 specifies nominal dimensions for various types, such as 1700 x 700 mm, along with their tolerances.

IS 6411

: 1985

gel-coated glass fibre-reinforced polyester resin bathtubs

CurrentSpecializedSpecificationBIMMEP · Sanitary Appliances and Water Fittings

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This standard specifies the requirements for materials, dimensions, construction, workmanship, finish, and performance of gel-coated glass fibre-reinforced polyester resin (GRP/FRP) bathtubs. It also covers sampling, testing methods, and marking to ensure product quality and conformity.

gel-coated glass fibre-reinforced polyester resin bathtubs

Quick Reference Values

Minimum thickness of laminate3.0 mm

Maximum water absorption0.20 percent

Minimum Barcol hardness of gel-coated surface40

Nominal length tolerance±10 mm

Resistance to stainingNo visible stain

Resistance to burning cigarettesNo visible damage

Minimum width of rim40 mm

Practical Notes

Ensure the bathtub is installed with the recommended support frame to prevent stress cracking and ensure load distribution.

Inspect the gel-coat surface meticulously before installation for any defects like pinholes, blisters, or discoloration, as these affect long-term durability and hygiene.

Verify the product carries the ISI Mark as specified in Clause 8, which certifies its conformity to this standard.