Maybe i should just do the one inch pipe down the 1 1/4 inch pipe and put the check valve at the top of the pipe before it goes into the pump?
Should still work right?
That should work. That is a more common way than putting a foot valve into a a sand point pipe. I think a one-piece plastic pipe would be better, because you cannot accommodate a regular coupling. If you use two pieces, you will need an inside coupling.. You can more easily get a long piece of polyethylene pipe. Anyway, with the topside check valve, you only have one critical long-term vacuum connection before the check valve.
On the other hand, can't you put a leak-free connection right on the sand point pipe? A tee at the top lets you sanitize. Then the check valve goes into the side port of the tee. A plug goes on top of the tee. So you have 3 critical connections -- the 3 ports of the tee, if your check valve has a male thread that goes right into the tee. You would use both PTFE and pipe dope both. Maybe the vertical pipe is known to leak, and that is what motivates putting the smaller pipe down the 1-1/4 pipe.
I was thinking about maybe having some poly with a 3/4 inch foot valve selected to have a small-enough od. Rather than using hose clamps to connect to something, you would run the 3/4 od male output of the foot valve (maybe with a nipple to get that) into the end of the poly. Then run multiple turns of stainless steel wire around the outside of the poly to provide compression, but to distribute that force to not cause the wire to cut into the poly..
I am just thinking. I have not done anything like this, and have never worked with a sand point.
So can you find a 3/4 foot valve that can fit inside a 1-1/4 pipe?