Hello, I have a somewhat strange problem. I own a single floor, 1250SF home built on a slab in Florida. In the master bedroom bath mostly, if I turn on the faucet to full hot I get warm only. If I leave it running and go to the tub 5 feet away and turn it on full hot for 3 to 5 seconds, the faucet water turns hot. I get the same issue in other rooms to a lesser degree.I have even tried shutting the cold supply off altogether and still only get warm. I have replaced the faucet with no change.

Can anyone point me in the right direction with this.

a faulty check valve in a recirculating system would be a good place to start.

I would start with the heater.... and work forward.
Best Wishes

How would i do that? I tried shutting of the water at the hot water tank and still had flow at all faucets on the hot side.

You need a licensed plumber. An onsite inspection and further testing will reveal all the answers to your questions. If you are still getting hot waters after you shut off the valve to the hot valve, you have bypass. Again, the plumber is necessary.

How long has this been going on?

Best Wishes

Tub or faucet valves that adjust hot and cold with a single knob or lever often have pressure balancers built in to help you avoid accidentally getting too much hot water. Sometimes these go bad and allow cross-over from hot to cold and vice versa. This can occur even when the valve is not open. So, one bad valve anywhere in your house could be affecting that faucet.

With the sink valve in question open to full hot, and the hot water shut off at the tank, feel the pipes coming in to each valve in the house. One may be permitting cold water to flow backwards up the hot water pipe.

Good luck. Let me know what you find.