The fixed hydration system can be a bit tricky to install the first time. This video from Hydrapak show you exactly how to install the fixed connector correctly
The fixed connector can be disconnected from the bladder using a pair of pliers. This can be done but we do not recommend doing it too much as it could shorten the lifetime of the connector.
The reservoir is made with a TPU film which is porous and can be stained much like fabric. If you use any drink that contains color, it will stain the TPU film and, although it does not affect the performance of the product, can make the reservoir look less then pristine. However, like fabric, these stains can be removed.
You can buy a product called Bottle Bright, that can remove these stains. This product is an all naturally based peroxide tablet that can be used on your reservoir and would likely remove the stains. This is their website and the video below show you how it's used https://bottlebright.com/
Bottle Bright is currently only sold in the US, but SIGG has a product that is similar in that the main ingredient is peroxide and may work too. https://sigg.com/en/accessory-cleaning-tablets/
The reason for the leak is usually related to the user biting too hard into the silicone. When the teeth hit the hard plastic piece in the middle of the bite valve your teeth could potentially cut through the silicone creating a cut. The best way to prevent this from happening is biting soft into the bite valve. The bite valve does not release more liquid when bit harder. If used correctly the risk of getting a cut is very low and a bite valve can last for months/years.