To the best of my knowledge it is a requirement to pass the CSA for approval to sell the unit in Canada.
That being said, I have over 30 of these under the previous name they sold under, Hagen 802 power heads, and they have been all underwater for as long as I've had them.
The oldest ones are 12 years old now and the newest ones are about 2 or 3 yrs old.
As for hooking a hose up to the output tube, I have some with a piece of 1/2" cpvc tubing that shoves into the output tube and then I push the clear fexible tubing onto the cpvc piece.
On most of them not used as power heads, I use 3/4" cpvc tubing shoved "over" the end of the output tube and then again use larger tubing to push over the end of this tubing. The larger tubing cuts down on flow restriction so this is my preferred way to go.
I have these power heads used as returns and as feeds for my DIY skimmers, routinely pumping to 5 foot heights.
One advice I would add and that is to once a month, dismantle and soak the power head parts in white vinegar, or diluted hydrochloric acid. (if you use vinegar, remove the O-rings first, and in both cases, if you leave the main housing in too long, like a day or more, then the acid softens the potting medium inside the housing)
Depending on how much calcium is in your tanks, and what the alkalinity is, the buildup of calcium deposits on the shaft make the impeller assembly rise up and the plastic impeller rubs on the rotating output housing, wearing it away.
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