dhponder writes:

Here's a link to a DIY one:

http://www.koiclay.com/diy/pg2.htm

Nice.

The one I own (brand name long since faded away) uses a simpler method to seal
the quartz tube inside the PVC pipe. Its a potting compound that I would guess
is epoxy. So each end has the outer PVC pipe, the inner quartz sleeve and the
epoxy and no other plumbing parts. They must use something to keep the epoxy
from running into the unit maybe a thin PVC disc glued in with PVC cement? It
wouldn't have to be waterproof, only hold the viscous epoxy until it cures (5
minutes).

Also, I have heard but not confirmed that acrylic tubes work as well as quartz
at much lower cost. Though I wonder why UV manufacturers don't take advantage
of this if it is true (or do they?). Perhaps acrylic eventually degrades/clouds
when exposed to UV?