balanced

There is (hot-cold) water everywhere in the two story (3/3) five years old duplex in Florida (with no freezing pipes or temperatures) but in the laundry room. Everything looks new and was properly checked including valves at the water heater. Outside meter replaced and pressure reducer valve checked and readjusted. Faucets OK. When the cold line is back flushed with neighbor's water supply (after cutting off my main line), water is not coming from the outside spigots but from the hot line in the same laundry room, and vice-versa. Someone suggested that it may be faulty balanced valves. Where usually are the valves hidden?