Warm Cold Water

Just looking for a second opinion. Had a inspection today and the cold water seemed warm so I took temperatures and it ranged from 88 to 90. I let the water heater heat back up and retested with the same results. The water would go from cool about 75 then rise to 88 to 90. The only conclusion I can come up with is there is a cold and hot water line crossed somewhere. This is a slab foundation.

Had this problem on a house I inspected the plumber found a shower/tub faucet that was leaking internal causing a cross connect and mine was a slab floor also these can be a B**** to find sometimes

Definitely reads like a cross connection. Was that one particular fixture or room, or the entire building?

It may be difficult to isolate, but easy to verify if it’s a “cross-connection” from a bad mixing valve or similar.

Turn off the supply to the water heater and run the cold-water for several minutes, then check it’s temp. Continue running the cold-water while you restore the supply to the water heater. If the cold-water rises in temp, there’s a cross-connection somewhere.