Thanks! Yes, those Plastomatic diaphragm check valves are what I would recommend using, and what I’d opt for if given the option. Though it’s probably only really needed on the SH supply, the OCD in me would want them on the water and soap as well.
I don’t have a link to where I’m getting the hastelloy check valves because I’m getting them through supplier for my day job company and I’m getting a pretty big discount through them. However, they are made by a company called Specialty Manufacturing Co and they have a website and it’s pretty easy to look through it and configure the check valves you want. They don’t make larger than 3/4", and they don’t offer it in PVC, which is less than ideal as well. Polypro doesn’t hold up as well in sunlight as PVC, so that could be an issue with a setup not covered or shaded. The diaphragm check valves are PVC. They may discolor slightly over time from sunlight/UV exposure, but it doesn’t degrade at all or lose any of it’s great properties.
I do think that 1/2" on proportioner is too small. But it’s the easy and cheap way to make a setup, and obviously it works well. It’s just not really what it should be. 3/4" would be great, and 1" might be best, though I’m not sure if there is any performance difference in 1" over 3/4". I’m still working on getting details between those. The issues are the 3/4" metering valves are harder to get, but 1" valves and components cost quite a bit more than 3/4".
I just placed an order for all the components to build the first setup, using 1/2" GF metering valves and 1/2" hastelloy spring check valves. Parts should arrive in 3 weeks (fittings in 1 day, check valves have 3 week lead time). Once it all arrives and is built, I’ll put up photos and everything for people to see and get feedback.
I’ll be ordering parts in a few weeks to build a 3/4" metering valve setup as well, but those valve have an 8 week lead time, so I’m waiting for the supplier to stock them again before placing an order.