Unless there's something I've missed there's no difference if it's laying
down or not. Perhaps if it is laying on it's side the waterproofing of the
bulb is exposed. For instance if it was up and down rain would hit the top
and then roll off the sides over any holes - kinda like a roof. If you lay
it on its side perhaps rain water could enter. A UV clarifier is just a
clear pipe with a UV light next to it. The water enters one side goes under
the UV light and then exits. You can build one yourself CHEAP.

Sam

Bampa wrote in message ...
I have been looking at many different brands f clarifiers for my 4000+
gal pond. Some of the more expensive larger units seem to specify
horizonal or vertical, but most basic units for 4000 gal ponds don't
reference the preferred orientation or the size of the units. I am
trying to figure where or how I would back fit a UV into my existing
some what cramped plumbing. Does it matter if they stand up or lie
down as long as the air gets out of them.

Also, I live in Minnesota, so I assume I would have to remove this
unit and take it indoors during Winter.