That vacuum break is on the supply side. There is 4 line under the sink 2 to the sink and 1 in and 1 out of the vacuum break. I never overflowed the tank I only filled it to 3/4. I guess I will have to try to follow each line, I don't know how because they are buried behind the drain inside blown insulation under the shower. I guess I could just replace all 4 from where I can access them. That would be a job. I will dry it out and try filling again to see if that was the cause.
I thought my house was unending maintenance.