We had the choice of jackhammering the floor across the whole basement to replace it at about $5000, or rerouting it and only jackhammering 10ft and thru the foundation. $2500 bucks later, all is good. Over half of that was labor, cutting into the slab and digging the new trench. first estimate seems a little high, the second one low enough to worry me.
The check valve is there to prevent the rest of the system (other peoples sewage) from backing up into your house. I would consider that important, and worth the extra to replace it.

Backup happened in the basement. Basement had a bathroom (w/ shower) and laundry room put in after the house was built. My guess is that the person who put those in put the check valve in because this plumbing was at much lower elevation than the house's original plumbing.

I think I should have the 2nd guy replace the valve. Worse case scenario is like you said: entire neigborhood backing into our basement.

I wonder if I can have him not repour the floor around the valve and just put a door/board/something down over it so the next time this happens maybe I could just replace it.

Assuming it doesn't cause ground water to enter the basement.

Why they would cover a mechanical fitting like that (which WILL fail) is beyond me.

I don't understand the difference in price for just removing it and replacing it. It seems to me, if you pay for the labor to dig in to the concrete and patch the pipe, the only difference is the cost of the check valve.

If you know where the fitting is and you are adventurous, you could probably do it yourself. The hardest and messiest part is breaking out the concrete. Replacing the check valve is a matter of cutting the pipe on either side and fitting in the valve with probably a couple rubber couplings.

Fernco couplings (sold at home depot):

Leaving access = bad idea (although one of the neighbors had same problem and had them make a hatch to access the new valve) because our water table is so high - in the spring it will just come through. Wonder what happens in the neighbor's basement?

The difference in price: there is none. I think the guy was maybe going to pocket a little extra for the cost of the valve or something.

There's now a hole in my basement and the company is overnighting a piece to fix the original valve because the valve they brought with them wouldn't work. They said it was too big or something (I was at work - wife dealt with them).

I found out that every house on my end of the subdivision has these valves just as a precausion because our houses are the lowest in the subdivision (although the earth keeps dropping and drains to a swamp across the street).

I'm hoping they finish today and the man cave can be put back together in time for football.

I've become less adventurous as I age. I know my limits now.

You are gonna be really pissed if that thing fails again.

A quick google search didn't find anything less than $500 bucks.

I would probably fashion something.

Maybe have the guys pour a nice clean squared off rectangle and embed some threaded posts (like J-bolts for foundations). Have a piece of 1/4 inch plate cut at the local steel fabricator. Set it on the posts to mark the post locations. Drill for the posts. Place a gasket down (maybe add silicone for good measure) and crank down the bolts. Cut the posts flush. And Viola!

You can check here for other ideas. These are the guys that will tell you ANY mechanical fitting will fail and needs access. I bet they have some ideas:

http://www.plbg.com/forum/list.php?1

it in your area. The reason for it is that if there's a blockage downstream from your home, sewage from upstream can build up and back up into your basement. If you're like most basements, there's a floor drain. If there's a sewage backup, it'll come into the basement through that floor drain. Cleaning up a sewage backup is not fun. I'd replace the valve. Truly. They don't put them in if they're not needed.