What exactly is protected under this patent US 20130001878A1. I have built a similar product but it's fill mechanism is automatic in nature.
Any patent protects what is listed in the claims -- no more -- no less.
The best way to start is to compare "Claim 1" word-for-word and see if your product matches the description -- if your product differs in just one matter of what is described in the first claim, then it is likely not covered.
Also, making something "automatic" could be an innovative enhancement and patentable in it's own right.