If your shower tray is not draining the water away as fast as you believe it should there will be an issue somewhere.
Again on occasion customers think this is a fault with the tray or the waste. Not so! If you check your tray waste you will see it is a large bore, 40mm in fact. If you have a shower bath it is usually a 32mm connection. Why then does the water not leave fast enough? Because on assembly the flexible waste hose has not been set to run off to house waste at a decline. In other words, you have a kink in the pipe or your pipe is going uphill somewhere. Reset this and problem solved!