maintenance, repair & replacement of filter media of iron removal plant installed beside pump house within sech abasancomplex, salt lake, sector-iii, block ff.- 1 replacement using new filter grade gravel 3/4 x 1/2 for iron removal unit. 2 replacement using new filter grade gravel 1/2 x 1/4 for iron removal unit. 3 replacement using new filter grade gravel 1/4 x 1/8 for iron removal unit. 4 replacement using new filter grade sand for iron removal unit. 5 replacement using new anthracite coal for iron removal unit. 6 replacement using new activated carbon for iron removal unit. 7 replacement using new pvc stainer 18mm x 50 mm for iron removal unit. 8 c.i. sluice valve with flanged ends drilled to as per i.s. 1358/62 and having all cast iron components as per i.s. 780/71 solid forged bronze inside screw spindle having ultimate tensile strength not less than 4.72 mt per sq. cm. spindle nut valve and seat faces of hard wear resisting, manufactured from best quality gunmetal conforming to i.s. 780/71, painted black all over with asphalt base paint tested to 21 kg (hydraulic pressure) per sq. cm., valve opening to anticlockwise direction, fitted and fixed complete.(i) 50 mm 9 supplying, fitting and fixing g.i. pipes of tata make with all necessary accessories, specials viz. socket, bend, tee, union, cross, elbo, nipple, longscrew, reducing socket, reducing tee, short piece etc. fitted with holder bats clamps, including cutting pipes, making threads, fitting, fixing etc. complete in all respect including cost of all necessary fittings as required,jointing materials and two coats of painting with approved paint in any position above ground. (payment will be made on the centre line measurements of total pipe line including all specials. no separate payment will be made for accesories, specials. payment for painting will be made seperately)(a) for exposed work (f) (ii) 50 mm dia. medium quality 10 painting with ready mixed black japan of approved make and brand including smoothening surface(b) two coats 11 painting with superior quality aluminium paint of approved make and brand including smoothening surface by sand papering etc. on steel surface :d)(b) two coats