Our products are not recommended for surfaces constantly underwater. The reason is that they work by stopping capillary suction and under constant water pressure the repellency is overcome and water penetrates via permeation and diffusion. The time it takes to overcome the repellency depends on the pore size of the stone and the water pressure. With a one metre pressure head it could take treated concrete 18 months but with 3 inches of water over porous bricks it could be days. Having said all that, if the stone is exposed to the air and allowed to dry regularly the repellency will be restored and the 'clock' starts again.

An alternative is a clear epoxy coating, although epoxies have a lot of other problems. If an architect or engineer insists on using an impregnator then make sure the entire stone is dipped sealed in STAIN-PROOF^® 40SK Consolidator & Water Repellent, formerly known as DRY-TREAT 4OSK™, and then when the stone is fixed in place apply STAIN-PROOF Premium Impregnating Sealer, previously STAIN-PROOF Original™. 40SK Consolidator & Water Repellent is a particularly good water repellent for low silica based stone. Note that make sure they use a special adhesive such as the Davco SE-7 and Davelastic to stick the dipped sealed stone to the bedding.