Plastic Pipe Stop Ends A Permanent Solution?

Hi, I'm hoping to get a bit of advice on some plastic stop ends I have installed in my flat. One in particular is used to cap off a pipe that used to supply the flat's hot water cyclinder from a communal water tank in the roof. The cylinder has now been removed hence the stop end. I don't have easy access to a shut off tap for this supply but I assume there is one in the locked roof space. While fitting some shelving near to the cap I knocked it and a drop of water appeared a little while later. Since then there has been no more leak. Should I be worried about these stop caps or are they generally reliable? Thanks in advance...

generally reliable, hit any stop end hard enough and it will come off. just make sure its either twisted correctly or the clip is in place to stop it coming off too easily