The first step with any leak, renovation or not, is to isolate the water supply if you can safely reach the stopcock or the relevant isolation valve. Turning off water at the source stops a small problem becoming a much bigger one.
During active building work, leaks are more often caused by a damaged pipe that wasn’t properly protected during other trades’ work than by a failing fitting — which is why it’s worth flagging immediately to whoever is managing the site, rather than waiting for the next scheduled visit.
We test and inspect pipework at each stage of a project specifically to catch these issues before walls and floors are closed up around them.
