The house is on city water which normal pressure 50 psi. This is a new hook up, one year ago. When home is left for the weekend there is high pressure built up 125 psi. Once a valve is turn on all back to normal pressure. Some one told us there could have been a check valve put on by the city or on the city meter and the hot water tank now builds high pressure. Is this true? What's the correct fix? bjr23