PVC pipe welding.

[Tonyz]

wanting to expand my aquaponic system and thinking pvc welding may be cheaper than buying lots of joiners etc esp when reusing pipework. There are a lot on youtube but its all big pipe work, I used to be a welders TA on plastic(?) pipe used for gas mains but that was one big sucker.

Has anyone used 'successfully a heat gun to expand 20mm - 45mm pipework?

[BobL]

What sort of plastic was it.

I've welded PVC, HDPE and PP but there's a much narrower temperature working window with PVC.

It starts to soften between 85-95º but it starts decomposing at 125-140º and above that it sort of chars.
It's OK for situations like negatively pressurised systems like fume or dust extraction system but I would not be putting any of this under pressure unless you had a lot of practice.

As far as using a heat gum and expanding PVC check this out.
Check this out
http://www.woodworkforums.com/f200/improving-machine-cabinet-dust-ports-187936/3#post1996096
http://www.woodworkforums.com/f200/improving-machine-cabinet-dust-ports-187936/5#post1999606
I've also done it on 50 mm pipe so can't see what it would not work on smaller pep.

I haven't posted it anywhere but I have made some chuck jaws that expand 100 mm PVC to make a joiner this way.

One thing I know is making bends is not so easy - Are you really sure its worth making 25-45 mm fittings as they are dead cheap.