Many plastics are very susceptible to UV. Polyethylene becomes brittle, PVC
has UV inhibitors, like carbon black or titanium to prevent degradation, so
depending on the type of plastic, it could be seriously affected and split
or crack, allowing water to the bulb and the electrical connections.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html


"Andrew Burgess" wrote in message
...
quartz and most plastics are transparent to UV. Ingrid

If so then the tube is very cheap. Tap Plastics has 1" dia x 1/16" wall
six foot long tubes for $4.30

In good units, the most costly part is the quartz sleeve, about 2x the
light.

See above. A brief web search finds a 40w UV bulb for $50. A little
PVC and epoxy, and a ballast from the DH's desk lamp and off you go...

The same site (pondbiz, just the first one I found) has an assembled 40w
UV for
$253

Good point. As I recall, the Koi USA one used a plexiglas tube. Dunno if
thats cheaper or not, or how transparent to UV it is...