The intake side has got to be free of most complications, but there still can be pressure to recon with. I have assumed that there is not enough pressure to worry about, but the check valve from www.ryanherco.com
is great! I didn't know where to get a fluid check valve. Looks like a great site! So I may have overpaid for a T that doubles as a check valve, but I'll save money in the future on liguid flow problems using them as a source. Thanks.
All that said, if someone is willing to try it, I'll wager that a peristalic put deals well with the back pressure issue, and will not flow in reverse because of it. I guess the real danger is just something happening to your setup, and draining your tank. Check valve sounds like a necessity, not for pressure, but for safety.