In reply to LastBoyScout:
Why not just get one but that is as big as you need? Linking a bunch of them together, dirty water, check valves... it's all just more and more potential points of failure in the system. I would go with kiss on this one.
Also, proper quality, reliable check valves are expensive, cheap ones are not reliable. I think you might be on a road to nowhere trying to find a cheap but good quality one.
Commercial waste for small and medium businesses is often removed in 1000 litre metal containers on wheels. You should be able to get hold of a trashed one of them for free (my next door neighbour has about 4 or 5 lying around outside his house converted into various things), it'll be the wheels that are broken but obv you would take those off anyway. If it leaks, you can always line it with a plastic sheet from any old DIY shop for about a tenner.