Tax rate on hardware, pipes and fittings is 18% with full Input tax credit.
Item falling under the chapter heading 3917 such as:
TUBES, PIPES AND HOSES, AND FITTINGS THEREFOR (FOR EXAMPLE, JOINTS, ELBOWS, FLANGES), OF PLASTICS - TUBES, PIPES AND HOSES, RIGID: OF POLYMERS OF ETHYLENE:TUBES OF POLYETHYLENE
For more details you can search item with HSN code for goods falling under this heading.
Tubes, pipes and hoses, and fittings therefor, of plastics under the chapter  are to be taxed at 18% with full ITC.