My bathtub hot water faucet has a leak, and I cannot find any valve to turn off the flow to the faucet. If I turn off the water to the hot water tank, would that damage the tank or cause other problems?

labman

That is OK if the expansion tank is, as it should be, after the inlet valve.

If you follow Bishop Chuck's suggestion on adding shut offs, make them ball valves. They are easier to work, give a tighter shutoff, and leak less.

labman

Since you have an expansion tank, it will be OK Water or air must always be free to flow in and out of a hot water tank to accomadate temperature changes. Ken 297 is not only wrong, but dangerous to suggest just shutting the inlet off without knowing you had an expqansion tank. One more reddie from somebody whose dangerous advice I criticized. The people coming here for help would be better served if more questions were left for somebody that could give a good answer. I seldom answer plumbing questions unless I see a bad answer like Ken's

The air in the expansion tank will push water out until air reaches the outlet.

Ken 297

Can you explain how this is dangerous in any way?
If you shut off the valve before the tank and water expands the expansion will be taken up at the leak in the bathtub. If you shut off the water after the tank expansion will be taken up through the inlet side of the tank.
If you shut off both sides of the tank the water is already hot,so expansion will be minimal. In the unlikely event expansion causes pressure to build up that is what the pressure relief valve is for.
If you are worried about water draining from the tank without the power being shut off I shut off literally thousands of hot water tanks a year with the power left on and have NEVER had a problem.
I honestly don’t understand what the concern is in my answer. If I am missing something in the original question let me know.