The best water proof duct tape?

[artnews300]

Hi
My story really quick, I live in a loft in a pretty good condition, but it does have some leaks around windows every now and then. I have used some special cock to fill the cracks - but you know water it always finds it's way somehow. I want to put some really heavy duty duck tape (Black or dark brown, as the color of the windows around it) on the top of the cock to minimize the possibilities for water drips. Again I am not talking about any crazy water leaks just minor. Also I know you'll say this is just a bandage and not a permanent solution, but i am renting and unless the landlord decides to fix the outside of the building, anything will be temporary. Any ideas what would be a really good tape that can last several years more or less.

Thank you

[HayZee518]

About twenty years or so ago I used a compound called MORTITE. it a very sticky caulking that came in a roll that you would peel off a length of"caulk string" off the roll and use it where you needed to. It plugged air leaks very well. It is waterproof and doesn't break down in the presence of water. for a great duct tape try GORILLA TAPE. It is very sticky and heavy duty.