Bath leak underside of plug hole

[jackpot]

Recently fitted a new bath and everything is fine until you fill it up and let the water out.
The underside of the plug hole is leaking slightly where the waste joins up to the bath and the plughole. This is only when the bath is pretty full so i think the pressure of the water when the plug is lifted is causing this.

Will silicone sealant solve this around the seal under of the waste fitting?

To tighten the joint there is a notch actully in the plug.. I can not tighten this any more so the rubber seal must not be adhering to the bath properly.
Thanks

 

[vinniejones]

Take it all to bits. Dry everything carefully, then a smear of silicone on every surface and reassemble,don't over tighten.