I installed a new Hudson Reed tub faucet on a tiled deck. This unit has the faucet being fed by two remote handles. The faucet also has a diverter valve that sends water to a handheld shower.

My problem is that this Hudson Reed unit uses 3/4" hose type fittings with flat washers (just like a garden hose). I cannot get all of these fittings to seal, 3 out of 7 fittings continue to leak no matter how much I tighten those three fittings.

This seems to be a problematic way to make a plumbing connection, how can I make these fittings seal? Once I get these to stop leaking is this a connection I can trust over time?