In order to choose the best bathtub heater, you need to consider what size bathtub you have, what type of pump you have, and what additional items you might need. A bathtub heater can be added to many types of jetted tubs, and the size of your bathtub will be important in determining which heater is best for you. In many situations, a heater is very easy to install, but you have to make sure that you get the right kind of heater for the pump system you have in order for everything to work smoothly together. There may also be some additional features available, and you should consider if any of them are important to you.
As you are looking at bathtub heaters, make sure you pay attention to how much power each one has. The more water your bathtub holds, the more power you will want your heater to have, and some models will even provide you with guidelines about how much water they can efficiently handle. Another size issue to consider is the size of the existing plumbing on your bathtub. Since you will be connecting your bathtub heater to the pipes that are already there, it is important for them to be the same size or of compatible sizes. You may find universal heaters that should work with any style and size of bathtub, but it is always a good idea to know what system you have and to make sure that what you buy will be compatible with it.
An inline bathtub heater replaces a section of existing pipe in your pump system, while a tee-style heater attaches to the top of your pump. The best way to determine which one is best for you is by looking at where you have the most space. If you don't have enough pipe to tie in an inline model but do have space above your pump, then a tee-style would be the best choice, but if you do have enough pipe to tie into and don't want to add extra bulk to the top of your pump, then make sure you get an inline heater. Be aware that if a heater is run by a pressure switch, it has to be installed on the pressure side of your pump, but if it has a vacuum switch, it goes on the vacuum side. You might find that one side of your pump is a more convenient place to install the heater and you will need to make sure that you get the right kind of switch to work on that side.
Some additional features that may come with your bathtub heater are fittings and hardware for installation, a longer power cord, or convenience features such as a heater indicator light. In most cases, these items are not necessary to use the heater, but one or more of them may prove to be helpful to you. Pay attention to what is included with your heater and to what items might be helpful to have because different models come with different features.