Yes, the installation you pictured is incorrect. It can be installed with barbs facing up, or vertically with the water going in the lower barb and out the upper. Disregard what others said about it not mattering. If we think logically the water surrounding the quartz sleeve will absolutely increase the contact surface area between the UV light and the water you flow through it. Sure, it won't blow up if its running mostly dry like it does when the barbs face down and water runs only under one side of the sleeve, but you'll be getting little to no utility out of its sterilizing function relative to a correc orientation at the same flow rate. I've installed 20+ UVs at this point and the principle holds true across the board of various brands etc.When I lift it on the side facing vertical the water has a hard time coming out. I turned on the UV light and I can see the bulb. There is no water around it. So it’s like the water is going in then running along the bottom and coming back out .

