Is it possible to restrict the tub flow similar to showerheads?

The issue I am trying to solve is running out of hot water when I fill the tub. My hot water is provided from the furnace. I don't have a stand alone water heater and don't really want to incurr the expense of installing one. When I shower, I never run out of hot water as it seems to be generated quicly enough by the furnace. My thought process was if I could slow the flow of water into the tub I'd be able keep hot water coming out instead of having to shut off the water and wait for the furnace to kick on. Oringally I thought maybe the furnace wasn't "sensing" that I need the furnance to turn on sooner in order to maintain enough hot water flowing.

I'd love to have an opinion on this subject. Many thanks.

flow

If you have a shower over the tub, trying to restrict the flow would cause the tub and shower to operate at the same time while filling the tub. Just don't turn the water on "full" when filling the tub. It makes very little difference whether you put 50 gallons in the tub in five minutes or fifteen, it is the same water and will be approximately the same temperature when you get done.

Yes, good point. I should have mentioned that the water dial is either "on or off" and you only have control of the temp of the water coming out. You can't control the flow volume with the water dial. Any other suggestions?

flow

Yes, but it is too late now. If you had asked before installing it, I would have recommended a valve such as the Delta 1700 series that has a volume control handle coaxial with a temperature control one.

It seems to me if you slowed down the tub fill, the water in the tub would cool off faster than you are running in hot water. Stick to showers!