Check valves

I just bagged my 93 mazda. So, I have a question I have a check valve from my compressor to my tank. So should I put one from between my tank to my and my valves.

I was just looking at check valves and saw that the air can backfeed into the tank when running low on pressure. I read this on a couple different sites. I don't know if it's true or not since my truck isn't baged yet but I guess it wouldn't hurt if you had the extra money.

It depends on your valves. Some require back pressure (my SMCs do for example). One way to find out is to fill your bags up then drain the tank. If your bags deflate as the PSI drops (usually ~30 psi on an s-10 w/v6) then you should consider using check valves. One thing to note is the diameter of the check valve's oriface is usually rather small. I have a check valve on each corner of mine and it considerably slowed down my lift speed. In fact, so much I opted to take them out (after I realized 1 wasn't working anyways). They can be a life saver if you loose tank pressure for some reason though. But some valves do not require them and will hold pressure from flowing back.