hot water heater capacity for bath tub

I notice that most MH come with 6 gal. tanks. Some have 10 gal. Does anybody know if the 6 gal. tank will supply enough hot water to fill a tub (not a garden tub) to about 3 or 4 inches? If so, is there any left for other use? How long does it take to refill the tank and get the water hot again.

Dwight Black


Senior Member
hot water heater capacity for bath tub

Depends on the size of the tub, and whether you are using any cold water at all while filling.

I suggest an experiment, using old milk cartons (or other known measurement) of water to pour into the tub to the desired level. That will tell you the total number of gallons of water needed. If that is not practical, then measure the tub in cubic feet (Length x Width x Desired depth - ie .25 to .33) and multiply by 7 to get the approximate total number of gallons. If you really want to fill the tub with hot water, than this is the answer to your question.

If you are going to be using some cold water, then you can figure out how much hot water will be needed with the

Hot Gallons = Total Gallons X (Desired Temp - Cold Water Temp)/(Hot Water Temp - Cold Water Temp)

For instance, if you need 6 gallons at 83 degrees, and your hot water is 100 degrees and your cold water is 50 degrees, then you will need 6 X (83 - 50)/(100 - 50) or 4 gallons of hot water (with 2 gallons of cold, of course).

This does not, as you might think, leave 2 gallons of hot water for other usage. As you removed 4 gallons of hot water from the tank, 4 gallons of cold water rushed in to take its place, lowering the temperature of that 2 gallons. How long does it take to recover? I'll leave that question for people out there with more experiance than I.
hot water heater capacity for bath tub

John has the math down for the # of gallons. I can say that on LP the water heater will recover faster than on electric but you can use both at the same time to get even a quicker recovery. I can heat 10 gallons to 120 degrees electrically in about 20 minutes. On LP I can hat it in about 15. You could in a pinch heat some water on the stove too!