Can a snake be put through a backwater valve without damage?

If your really lucky. I wouldn't suggest trying it because you may not be able to get the snake back out. I would suggest removing the guts of the valve and snaking from there.

MGD77 is right on. You will be able to put snake IN - but good luck getting it OUT.

Can a snake be put through a backwater valve without damage? m Both experts are bang on.
Your sewer check valve, (see image is like a roach motel. The cable can enter but it won't be able to come out. This can be done in one of two ways.
1) Milos suggestion
I would suggest removing the guts of the valve and snaking from there. **OR**
2) If the clean out's in front of the check valve you can snake from there.
Good luck, Tom