I have a filtering system with a bypass and one of the valves was badly installed and it also leaks through the handle gasket. The valve is in a system that looks like this:
The encircled area is where the problematic valve is. As you can see, it would be very hard to cut the line and add a new valve, because I cannot bend the main line too much. The valve is cemented to the pipe and threaded to the filter (the blue rectangle), but connected to the main line with a cemented T-shape fitting. In other words, I cannot just unscrew it, as it is permanent. What options do I have in this situation, without needing to do the entire system?