A couple of months ago I fitted a waste disposal unit to the kitchen sink, I checked first and as far as I could find out I did not need to make any changes to the drain system.
A couple of weeks ago we found foul waste over flowing from a manhole in the garden, we got a plumber in to rod it out and it cleared no problem.(we only knew there was a problem because the down stairs toilet was draining slowly after flushing. I am now a bit worried in case I have not done something I should have done, or is it just a coincidence. (I think the manhole goes into a main drain that carries waste from other houses apart from mine). I don't want to find in 6 months time that I have completely blocked my local drains!