Stained Seams

Stained Seams | Print Version

Stained seams have been observed on finished linings. They range from small dark spots in the seam center to dark patches which appear to emanate from seams.

Causes: Seams become stained due to water passing through the liner either during cure (hot water passing out) or after cure (groundwater passing into the liner). When hot water passes out, spots or stains are sometimes caused by impurities being filtered out of the water. Also, if water can find its way under the seam tape, it may track along the seam causing impurities to be filtered out in the seam area for some distance.

If seams become damaged during installation it would then allow water to pass out during cure and back in from the ground following the draining of the curing water.
It is also possible for resin to find its way directly underneath the seam tape and under certain conditions, to cure in such a way which causes small holes in the covering tape to melt along the edge of the white tape.

If the liner is porous due to poor impregnation or monomer boil then at a later date the water may be able to find a path from the groundwater to the inside surface of the liner depositing oxidized iron/manganese salts on the the surface of the coating.