HYDRO-BLOK Seals for Pipes & Mixer Valves HYDRO-BLOK Shower Seals allow you to fully waterproof your HYDRO-BLOK shower system at shower heads, mixer valves and tub spouts etc without using sealant. Constructed from a high-quality waterproofing membrane and over-molded, stretchable rubber gaskets. Simple installation with a thin layer of thinset prior to tiling (see packaging for complete instructions). – Fully Waterproofs your HYDRO-BLOK Shower without the need for sealant – Simple & Quick Installation – Stretchable Rubber Gaskets seal tightly – Install over existing pipes or valves without the need for plumbing changes – High quality waterproof membrane provides a fully waterproof barrier in conjunction with your HYDRO-BLOK Shower System