Andy
Peccavi is as usual on the money. Maybe try with boiling water first if you can get some of the water out so the hot water gets to the fats. As a tip in future as you seem to be using this as a sink waste too throw a kettle of boiling water down it every so often to remove any fatty depisits, don't treat your sink as a waste disposal and try to lower the fat content of your wet waste.
kennyf, March 2009