Leaks can be worst thing for your map, very much drop fps and no shadows at all. A lot of new mappers release their maps with leaks, this is not so good, map performance is poor and visual is porr also.

What is leak?
Leak is a hole in your connected to hammer space.


How to fix it?
Fix 1. Search in your map all holes connected to the space.

Fix 2. In hammer go to Map / Load Pointfiles


Load map .pts (point file)


A new line is loaded all over the map, follow the line from the blue point.


This line somewhere will cross betwen map and space, can be in the red end point.


Fix the hole and leak is gone, for ever