Dry tops and dry suits as well as other “dry” kit are treated with a DWR finish. DWR stands for Durable Water Repellency. This is the treatment that makes water form as droplets or beads on your kit. When this starts to wear off (which it will) your kit will start to soak up the water. This may not make it through the laminated layers of the fabric but it will comprimise the breathability and effectiveness of your kit. This is known as “wetting out”.
This DWR treatment can be taken care of with a DIY treatment of Nikwax or similar. The first step is to make sure that your kit it clean. Water and pure soap flakes/liquid will work just as well as the fancy stuff you can pick up in outdoor stores. Once clean the kit can be treated with something like Nikwax.