Abstract: Described herein are solid compositions for water treatment of swimming pools and spas. The solid composition comprises, in a single solid product in the form of a tablet, puck, briquette, a capsule, powder mix or the like, a combined source of a plurality of chemical compounds such as chlorine, algaecide, clarifier and pH adjuster. In embodiments the solid composition comprises at least a combination of (i) a source of chlorine for killing bacteria and (ii) a neutralizer for ensuring a proper pH balance. In embodiments the solid composition is be formulated as a bilayer. In embodiments the solid composition is formulated as a bilayer, a first layer comprising sodium dichloroisocyanurate (NaDCC) and a second layer comprising trichloroisocyanuric acid (TCCA).