Water Heaters - Getting "more" hot water out of my water heater?

Ever since we moved into the new house the water heater has been unable to fill the big corner tub in the master bath. (By "fill" I water up to your waist and be hot, not just lukewarm.) I've even bumped up the thermostat and it still isn't enough for a nice full hot bath.

First off, I have no idea how many gallons the tub holds. It's your standard corner tub. No whirlpool jets, nothing. Just a "plastic" tub.

The water heater is a State "Select" PR64ONORT 40-gal gas unit.

Does this just sound like the water heater is undersized for the tub?

Also, the water heater and tub are on exact opposite corners of the house. The basement is unfinished, so it stays ~60F. Seems like that would have a significant effect on the water temperature that finally comes out of the faucet. Those flexible plastic tubes (the red and blue ones) are just bundled all together, hanging below the floor in the basement.

Ideas? Hopefully other than replacing the practically new water hater?

OK. A 40 gallon heater will yield about 26 gallons of hot water (about 65%). This is due to the mixing of incoming cold water with the hot water in the tank. Yes, your water heater is too small for the job. It appears that turning up the thermostat is still not giving enough water (always use caution with high settings).

You can either replace the existing heater with a larger one, or add another heater with your existing unit.

Can you add another heater closer to the tub? The long run is also hurting you.

Too small!

Well, crap. That's the answer I was afraid I'd get.

How difficult is it to add a second heater?

Is there anything else I can do for now, like adding insulation to the heater and/or pipes that would make a noticeable difference w/o costing much money?

Probably not. Insulating the lines is a good idea, though. Check to see whether insulating the water heater is prudent before doing it - is it warm to the touch? A lot of newer ones are pretty well insulated already.

It wont be easy, because the flue pipe, and quite possibly the gas supply pipe , may need to be changed to support a second WH, or a much larger one. You could certainly go to 50, which would help, and possibly to 60 gallons, but that would be about it.

You might want to look into an electric tankless model just for this tub. You wouldn't need a big one just for the tub, and you wouldn't have to worry about running new gas lines and a flue. It would be an expensive option, but I'd bet you'd be happy with the results.