On Wed, 16 Feb 2011 01:33:22 +0000, John Rumm wrote:

Could you not stick a solvent weld elbow on instead - that won't come
apart!

Not as easily thats for sure but may well break something elsewhere.
The forces excerted by expansion/contraction are considerable.

Not sure that the coeffcient of expansion of ABS/PVC is but on an 8'
length I wouldn't be surprised to see 1/2" or so over a 30C
temperature range.

How about cutting the pipe in the middle removing 1/2" or so and
joining with compression coupler? Then think about where the pipe
needs to be "fixed" to get the expansion taken up in the compression
joints and hopefully not "walk out".

--
Cheers
Dave.