Ive built a couple. We dont have those fill valves like you posted here. Ours are plumbed from bottom. I did have to though buy an adapter from an aussie on ebay. 7/8 or some wierd shit like that so it could be adapted to 3/4 hose. But shitter valves work just fine. And when they crap out they give suttle warnings. Bonus is hardware stores have thousands of them. So it can be replaced without tools in homers parking lot. Sorry lowes parking lot. Fk homedepot. Stupid covid rules.You are hilarious!!
This is obviously a conspiracy!!!
Another pretty solid fill valve is a Hudson. Still about 15 bucks at tsc. Its already set up for 3/4 pipe thread. They use these for pressure washer tanks and to fill troughs for cattle. They take away at least 7" of your tanks capacity to work.
The down side is chem. If you like mixing chem then you need to get creative.