I have a leak from my shower, it's coming down into my kitchen. I've had the sealant, waste pipe and tray all checked. I've also had the shower controls checked. Weird thing is the shower leak only happens when there's weight on the shower tray. The shower tray doesn't flex in any way, which is odd. I wonder whether there's a pipe under the tray that only leaks when I'm standing on it; the tray is raised off the floor. I've also tried pouring buckets of water in the shower when I'm standing on the tray, but this doesn't work. The leak only happens when the shower is on and I'm standing in the tray. West Mids. thanks