In article , Andrew
Mawson Sat, 31 Dec 2005 12:40:23
writes

In my experience caustic soda is good for fatty deposits - kitchens
etc, and sulphuric acid is good for hair balls - baths & showers.
Beware that sulphuric acid will stain baths and shower trays so be very
careful how you pour it.

Quote from http://proterraonline.homestead.com/homecare_drains.html

Although it is sold commercially as a drain cleaner, never use caustic
soda to open a drain. It will combine with the grease from soap or food
wastes to form an insoluble compound. Potash lye or caustic potash may
be added to finish opening a drain, but never use them on a completely
stopped up drain. They may take as long as overnight to work, and if you
ultimately have to open the trap, the chemicals would be a hazard.

Maybe US soap and food is different??
--
Les Desser
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