For some reason I'm not getting hot water from my bath tap. Everywhere else in the house in fine. We have a gas hot water system which heats water as needed. When I turn on the hot tap in the bath it gets very hot then runs cool. Any ideas?

Does the insta-hot feed any other fixtures other then the tub? If not I would suspect the heater. If It supplies other fixtures I would shut the water off to the tub, open up the valve and pull the cartridge to ckeck and clean the inlet ports on the cartridge. Before you reassemble turn the water on to flush out the supplies. Now reassemble and test. Good luck, tom