My new land is big, but good portion of it is shady. And not whole sunny land is usable - part of it is taken by septic field. After investigating septic plan I decided to make a decorative strip of flowers between the road and the leach field (don’t want edibles close to either leach field or road ). The septic pipe is located right on the corner of that future strip and is an eye sore. I know there are decorative covers for septic pipes, but I am not ready to pay ~$300 for that. My idea was to place trellis around the pipe and plant clematis on it. I am thinking to build a pressure treated frame 8’ tall, with a 2’ square in base and top and some pipes as legs that will go in the ground. Then close sides with PVC lattice and place it over pipe. I can plant three clematises around it. The question is, how it will behave in wind when thick grows works as sail? Normally I wouldn’t be too worry, if it fells in strong wind, I can set it back. But with pipe inside, will the fall damage the pipe? I just do not know how stable it is. I can probably use wire from top to the ground, but it possible only on two sides, on other sides it will be on the way of lawn mover and my DH will not be happy. According to plan, the vent is the last object of the septic system, pipe coming to it is perpendicular to the road and ends with vent. As my trellis will be 2’ wide on all for sides, I can drive the metal post deep enough to be stable 1.5’ from the pipe in direction to the road(where I shouldn’t hit anything) and then connect the trellis to it. The trellis will be placed 0.5’ from vent on one side and 1.5 on another side. Will that be enough to protect the vent?
Attached plan and photo of the area. On the plan the light grey drawing I suspect is an old system, that was replaced. New system is black ink. The septic was replaced right before the sale.
I think your basic scheme is sound. I also think the vent pipe is strong enough to withstand pressure from wind if the clematis makes a sail. It might also be possible to connect the bottom of your trellis to the bottom of the vent pipe with wire and the top of the trellis to the top of the vent pipe the same way. You can test the pipe for rigidity and possibly reinforce it if necessary by digging around it and burying large stones around it.
Or you could paint the pipe brown or mottled and plant a shallow-rooted bush by it. I’m not sure how deep is safe to drive a pipe or post without damaging anything. You might check with the septic company. Find something deer don’t bother, if there is such a thing.
I was thinking about painting, but the prep work is a lot and even in this case I would probably have to repaint every year. And, I need some place for clematis! 
Just get a can of oil-based spray paint. I sprayed PVC pipe bird houses and the paint is still sticking fine after several years.
Easy-peasy and ready for clematis. Looks good.