Eh, just get one of these and be done with it.
I get what your saying about the union now, for some reason I was thinking a standard slip coupling. Is a union rated the same as straight PVC for pressure? I would worry it would leak like a sieve at pressure. I feel as though a ball valve will do approximately the same thing with the seal involved, although I have never heard of using a union as a safety pressure release for a potato cannon. I know you can get brass release valves for reasonable prices that would be smaller than a union.
I'm a comp sci, so you got me outguned when it comes to fluid dynamics. I'm sure there are plenty of youtube videos and plans that will show if a 1.5 ball valve has a big enough hole to avoid a slow release.
I get what your saying about the union now, for some reason I was thinking a standard slip coupling. Is a union rated the same as straight PVC for pressure? I would worry it would leak like a sieve at pressure. I feel as though a ball valve will do approximately the same thing with the seal involved, although I have never heard of using a union as a safety pressure release for a potato cannon. I know you can get brass release valves for reasonable prices that would be smaller than a union.
I'm a comp sci, so you got me outguned when it comes to fluid dynamics. I'm sure there are plenty of youtube videos and plans that will show if a 1.5 ball valve has a big enough hole to avoid a slow release.