I would never even dream of modifying a UV unit, because of the inherent danger of doing so. Those units have intense UV inside, in the UV spectrum where it can damage you as much as the bacteria if you get exposed to it. It also has electric parts in direct contact with water, another thing to be careful about modifying. And, the UV tube is made of quartz, not glass, to avoid being damaged by the UV - even a finger print on the quartz can cause it to shatter from the UV. UV is dangerous. UV units are not suited to be our DIY starting point.