Its important to note that the automobile windshield chip repair exterior trim and moldings that we can see on the outside of the glass are for looks only. The actual water seal comes from the "urethane" adhesive which is used to create the bond. Its in this urethane that the water leak is originating.

Good question. Windshield crack repair equipment varies widely among companies. High quality resins, injections and air removal methods vary from company to company and can affect the finished repair. Quality injection units and high quality resins are as important as the technicians performing the crack repairs. The quality resins create stronger bonds and resist yellowing better than inexpensive resins. Quality injection equipment will remove more air and the injection capabilities provide a higher quality crack repair.
The main question when you are seeking to fix a cracked windshield is whether to replace or repair the glass. Most auto glass shops will opt to repair a crack or chip, as long as it is not directly in front of the driver. They will use a clear resin that is dropped onto the crack and then fixed with an ultra-violet light. The clear resin will then cure and the crack will no longer be visible to the human eye. Most cracks or chips can be effectively fixed in this manner. This method can fix small cracks as well as larger spiderweb style cracks. If an actual hole is formed in the windshield or the crack has traveled too far, your best bet is windshield repair near me.
Now you have 3 options. You can pay out of pocket, you can have your insurance company cover the cost, or you can do the repair yourself. The cost out of pocket will vary from $30-$60, depending on the company you chose. Filing with insurance is easy because it is no cost to you, and the auto glass repair company deals with the paperwork. You can also attempt the repair yourself, but if you do not feel comfortable, i would suggest calling a professional. There is a good step by step windshield repair Instructable available, as well as other information online.
The hole in the adhesive disc should be pushed out and the paper backing has to be peeled off. The disc has to be centered over the area proposed to be repaired, press it on the windshield using a tab present on the disc facing upwards.
But the best way to fix a leak is completely removing the glass and shooting a new seal. This is the only way to truly see what is happening. If the glass is removed a technician can 100% fix the underlying issue. This option may require the purchase of a new molding. Also your auto glass company will most likely require you to purchase a new glass if the old glass breaks upon removal.