Is it possible to use a tankless hot water heater with a hot tub?

Well, put that way, I don't see why it wouldn't work, however, I would turn it down when not in it so heater doesn't run constantly.

Hot Tub Water Heater

I don't think this is a good idea. The purpose of the water heater is to heat the water. Once your hot tub is full, the water heater wouldn't be able to continue to heat it because that is not what it is supposed to do. The heater of the hot tub is supposed to maintain the temperature of the water. The water heater doesn't cycle water through it. It merely gets it, heats it and dispenses it.

I don't know how much a new hot tub heater would be but a tankless (or on demand) water heater will run you between $4-6K unless you have a friend that can put it in for you. You will also need to run a dedicated gas line run just for the water heater and still have power run to it as well.

Hope this helps.

Jacuzzi Hot Water Heater

Hello, I would like to know the model, and manufacture of your tub and the age of it. There's no way the hot tub heater replacement can be as expensive as a gas water heater. Pictures would be great if you could snap a few digital ones and post them on your question. Some hot tubs are heated via gas dedicated heaters made my Hayward, Jandy etc... That is an expensive way to go of course so I applaud your ingenuity. I can't imagine that the 5.5kw heater cost would be more expensive that the price per # for gas. Your tub sounds like it must be older and need some sprucing up as far as installation too. Another question is where you live so we know what kind of insulation is needed. I hope the cover is in good shape too to be able to retain the heat once it is created. (Very important) The biggest problem with your scenerio is that the temp will be very very hard to control. The average one produces a temp of 120 degrees, which of course is 16 degrees past the temp that is safe fo you to get into. Feel free to email me.

Not to mention the corrosive effects of the chemicals you need to use will kill off a non-pool/spa heater faster since they use Teflon or Tefal elements etc...for just that problem.

it would be way cheaper to invest in a portable baptismal type water heating devise similar to the one on the link.

they make one for heating tub water quickly but I could not find that site in my haste to answer. maybe your local hot tub dealer can get you one. The way it works is you simply stick it in the water and heat the existing water up. It does need a 220 receptical.

There is no such thing as a "hot water heater." It is a "water heater." You wouldn't heat water that is already hot! LOL

Other than that, it sounds like a reasonable plan.