Replacement Viton® seals pack for FAISPRAY16HD Professional Knapsack Sprayer. Replacement Viton® Seals are resistant to most acids and solvents, enabling the sprayer to be used with more aggressive chemicals widely used in automotive and professional cleaning and some agricultural applications. It is always advisable, where possible, to use a water-based product as these are less damaging to the environment. Use of aggressive chemicals will inevitably shorten the working life of these seals.