With due respect to RVPARKOWNER, much of what you say is immaterial.
Again; IF the OP has described the situation fairly.
If this problem happens when full in the summer it is not a new problem. They have an underlying infrastructure problem that needs to be addressed and that they have known about for some time. This is NOT the customers fault.
The OP stated they talked to the Maint. Man. The Office may have been closed by the time they figured this all out. And while I do agree that sooner is much better to let the management know about a problem it does not negate the fact that this was a well known issue at this park and a reduction - refund was certainly in order. Unless the OP was informed AT CHECK IN that there was a problem.
This appears to be simply a case of High-Season, Special Occasion Greed.