Several usages of a water test kit depend on the material of the product. If a product is made from paper (test strips), then you are sure to dispose of them right away. You cannot wait for it to generate another result once used already. If it is made from plastic, then it is safe to use it again. Products that are made from plastic are usually long-lasting. Still, it depends on the user. Glass products are also worth using for a long time. They may be fragile, but careful use will prolong it more. Simply wash these test kits after use. There are harmful contaminants that may have stuck in it. These contaminants can still affect the result of waters that are yet to be tested.