Should I clean the threads on waste pipes or U-bnds on sinks etc.

anotherquestion

Hi there folks, 
Its a simple thing but more often than not when cleaning the waste, or ubends on the sinks, I try to stay clear of cleaning the actual threads on these fittings as I have this idea that maybe the bit of dirt on there is maybe helping to seal the fittings and maybe a thorough clean of the actual threads would only create a leak, that's not to say the dirt couldn't create a leak too, but so far it seems to work for me, ill-wisdom or not?
Thanks.

Mistral001

The water seal is usually made by a rubber washer inside the joint and not the thread.  So clean as much as you want, it will not affect the water tightness of the joint.

TELLIT01

There shouldn't generally be any reason to disassemble the waste traps.  Much easier to use one of the many drain cleaners available.