We eventually got rid of the gun barrel in our house recently. It has a certain life expectancy (25 to 30 years max I think?) but it WILL leak eventually. If you're getting other work done, get it replaced now. The leak can start gradually, and possibly in more than one place, and it can cause terrible damage over time (carpets, wooden floors, walls, general dampness building up over time, etc). The price will depend on how extensive it is, and how easy it is to get at (is it buried in concrete floors?). Our plumbers recently charged us €400 per day for two lads and it took them nearly 2 days, plus materials. More expensive that I anticipated, but DON'T be tempted to turn a blind eye to it. The plumber even mentioned that some insurers will not cover damage caused by leaking gun barrel, so beware!