回复：多谢各位的意见。其实除了这个问题，我还遇上了下水道的问题

Again, you need evidence to show active concealment or misrepresentation. For the house value, assuming you are talking about the present value, not future value because you said you would not buy if for the crack, you may need an appriasal to show the house with/out the crack to find out if you have damage, therefore, a case.

For inspector, I don't know if you have a contract with him or what the contract says. I tend to think you cannot hold him liable for negligence or anything, absent of an express contract or any applicable state statute. The reason is that you have to prove that he is negligent. If a reasonable inspector would not find the crack, because the owner patched the crack up, why should this one be required to find? You looked at the house and you didnot see anything wrong, why should he? You may argue that he has higher standard because of his experience. My point is that it is really hard to hold him liable for any wrongdoing, absent any contract clause or state statutes. Try to search the law to find if your state have some kind of consumer protection act. Did you contact the owner? What did he have to say?

For the plumbing problem I don't think the owner has any responsibility because AT closing you accepted the house and there was no problem. Did you suspect any wrongdoing of the owner?