Plumbing – How to Temporarily Cap PEX Pipe While Laying New Flooring

The advantage of tiling first are that you don't have to cut as many tiles - just those at the room corners and around pipes. Certain areas will be easier to tile too.

The disadvantage is that you need more tiles. You will also need to make sure that all pipes are in the correct location but not connected. This will mean either having the water turned off or fitting isolation valves (of itself not a bad idea).

There should have been a 'packing' in the stem assembly. This is usually a gasket or a series of gaskets that prevent water from seeping around the stem when the stem is in the off position. If the packing was in good shape (no cracks or brittleness) and was seated properly then I would say it's time to replace the whole fixture.

In my past experience if the leak doesn't come from the stem or the packing around it, then the time finding the problem and the cost to fix it usually is not worth it for a cheaper fixture.