No Water Seal should not be used before plastering or in any interior applications. Water Seal will not seal a porous surface or act as a bonding agent to increase the adhesion of plaster. Water Seal can only be used on bare and uncoated brick, stone or concrete.Click to see full answer. Similarly, you may ask, can you apply Thompson’s Water Seal with a sprayer?Answer: The manufacturer of Thompson Water Seal recommended that you use their product with a plastic sprayer with a brass wand, such as our Chapin Premier sprayer. Once you are done with the product, it is recommended that you run mineral spirits through the sprayer and then water to clean it.Likewise, is Thompson Water Seal toxic to fish? Thompson’s is a horrible product and it’s not a true water proofer. It’s akin to putting silicone on your shoes to water proof them, as soon as you scuff the surface it’s gone. Of course it is also toxic to fish. You probably could however find a pool paint locally that is not toxic to fish. Also question is, how often use Thompson’s Water Seal? Applying a sealer and/or stain typically is recommended every one to three years, depending on the finishing product, deck use, weather conditions, and sun exposure. All Thompson’s WaterSeal products are DIY-friendly, and most need only a single application on a clean, dry deck.Is Thompson’s Water Seal any good?The key features of this product is that is prevents water damage, but it is not nearly as effective as other waterproofing sealer options. Other reviews of Thompson’s WaterSeal state that the product doesn’t last more than a few months, if that.