Inline Heater or Waterbed heater?


I missed a post last week. I’m sorry! To make up for it I’ll  be making two posts this week. Thanks everyone!

When the waterbed heaters underneath our Floatarium float tank died, the choice between waterbed heaters and inline heaters was an easy one. We weren’t about to completely disassemble the tank, re-spray foam insulator (the old insulation would have to be removed to get access to the old heaters), and then put it all back together. It was just too big of a project when such a simpler option was available.

But what choice do you make when installing waterbed heaters is just as simple as installing an inline heater? What are the pros and cons in choosing one over the other? Today’s post will discuss these questions and help you make the right choice for your float tank business.

What are the differences?

First, lets talk about the most common method of heating float tanks: waterbed heaters. Waterbed heaters are placed underneath the length of a float tank and keep the water at a relatively even preset temperature throughout the day. Most float tanks ship with these pre-installed.

Inline heaters are installed as part of a tank’s plumbing. It will heat the water in your tank only during the time in which the pump is running. Once a tank is at a preset temperature, the heater turns off, even while the pump continues to run. During a customers float, the water temperature is slowly dropping. This temperature change is so slow that it is imperceptible to the floater during a 60-120 minute float. This is where the pros and cons come into play…

The Tradeoffs

While a floater is not going to notice a temperature change during a regular length float, it will drop to an uncomfortable temperature level during extended lengths of time such as during an overnight float. A waterbed heater is going to continue maintaining the proper temperature throughout the night.

Waterbed heaters may provide constant temperature, but they will eventually die, and they don’t just flat out stop working, they tend to start making noises. Whether it’s a buzzing sound or a crackling, it will start out as an imperceptible noise, then gradually increase in volume. The number of floaters that will be affected by this before you find out and get a replacement heater is a number that makes me uncomfortable.

Speaking of replacement, while our Floatarium tank has a particularly odd design that makes heater replacement especially difficult, most float tanks still require a process that is both time and work intensive for changing heaters. Usually the entire tank needs to be emptied. Often times tape or some kind of insulation wrap also needs to be removed to gain access to the heaters (which then need to be replaced after the swap). Inline heaters have an easy removal system that is as easy as twisting loose 2 plumbing parts.

Waterbed heaters require electricity on and off 24 hours a day, 365 days a year as they maintain a specific temperature. Inline heaters only require electricity during the times your pump is run. For us, that’s about 8 times a day. We have to run our pump about 15 minutes to get it up to temperature in the morning (we already run our pump 20-30 minutes in the morning), about 3-5 minutes gets the temperature back up. A great plus is that we aren’t paying for electrical to heat our water at all during the evening. Similar to inline heaters replacing regular water heaters in homes, the electrical use is less which means your electrical bill is going to be cheaper.

Pro & Con List

Waterbed Heaters


  • Relatively constant temperature 24 hours a day


  • Difficulty swapping heaters
  • Slow “death” of heaters can mean unsatisfied customers and delay before replacement
  • Tend toward shorter life span

Inline Heaters


  • Complete silence during a float
  • Easy swapping of expired heating unit
  • Lower electrical use
  • Tend towards longer life span


  • temperature is not constant
  • temperature will not be comfortable for extended length floats
  • pump must be run at least once every 1-2 days so that the water does not crystallize.

What’s the Right Choice for You?

You will want to make your choice based on what type of business you own and what type of business you see yourself running several years down the road. For some, offering late night floats is mandatory to their business strategy. For others shorter operating hours are perfect for what they want. If you plan on doing late night floats, waterbed heating will be required. If it’s not required, you will want to look at ease of use and cost savings and decide from there.

Finally, a combination system is completely reasonable as well. While you can mostly depend on an inline heater for raising the temperature and saving on your electric bill, you could also depend on a waterbed heater to kick on if temperatures dropped too low which would make late night floats possible.

What kind of water heater do you prefer? Let us know in the comments below!

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12 responses to “Inline Heater or Waterbed heater?”

  1. colin roald Avatar

    If inline heaters use less power, it doesn’t seem like it can be that much. If you think about the overnight situation, either way you have to replace all the heat energy lost by the tank through the night. With a waterbed heater, you’re replacing it a little bit at a time at frequent intervals. With an inline heater, you replace it more or less all at once in the morning, but it’s still basically the same amount of heat needed. (A couple small efficiency effects occur to me: heat transfer is proportional to the difference in temperatures, so the rate of heat loss will slow somewhat as the tank cools down. That means the inline heater will have to replace a little less heat in the morning. But on the other hand, pretty much all the heat produced by a waterbed heater is going to end up in the tank, while an inline heater will more or less inevitably lose more to the room. Seems like you’d have to really do the measurement to figure out which is more efficient overall.)

    1. dave arnup Avatar
      dave arnup

      In line is massively cheaper as the heater is in direct contact with the water – waterbed heaters have to send heat through the tank before it gets to the water. As the owner of an i-sopod and previously a tank with a waterbed heater I’ve montiroed electrical use as noted that it is 2.1/2 times cheaper to run and that’s even more amazing when you consider the i-sopod volume of water is 50% more than my previous tank.

      You find that lots of tanks on the market have little or no insulation which means that they have to supply continuous heating just to keep the solution at the right temperature, which is both expensive and more importantly not very environmentally friendly.

      My tank is doubled skinned, with a large air cavity in-between which means it is exceptionally well insulated, so well insulated in fact that in one of our tests when we switched off the pod for 24 hours we only lost 3.7º degrees, which works out at a 3/20th of a degree an hour or 0.15

      The human body radiates between 70 to 136 watts of heat per hour, so what we actually find is that even though the pod isn’t being heated during the floatation session, because of the thermal insulation and the heat radiated by the human body the water temperature can sometimes actually go up by anything up to 0.5 a degree and this is for sessions of between 3 to 4 hours.

      Titanium flow through heaters heating element is actually in direct contact with the water which makes for a very fast, efficient and economical heat transfer. Under tub heating is slow as the heat has to travel through the fibre glass before it even gets to the solution; this can causes hot spots in the pods with hotter water at the bottom of the pod, you also lose heat and energy as water bed heaters aren’t directional – so heat goes out to the sides and also back in the floor which is wasteful. Also you’ll never get a waterbed heater big enough to cover the whole surface area of the base of the tank, again leading to differences in temperature.
      I noticed when I removed by waterbed heated tank that I had scorch marks on the floor where the heat had gone down as well as up!

      I have a thermometer which has the temperature probe on the end of a long wire and I’ve tested extensively through my solution and the heater is a constant temperature through the solution. I think having a big powerful pump ensures a good mix. My waterbed heater tank in comparison was always much warmer at the bottom of the tanks solution than at the top.

      Again because of the design of the i-sopod, the saline solution is heated outside the tank eliminating the electro-magnetic fields which occur when embedded heaters are used. As a result our customers have found that the overall quality of the floatation experience is vastly increased.

      Because my tank is only heated when it’s being filtered the pod is effectively switched off when it’s being used, with only a low voltage of 12 volts being supplied for the internal lighting, the attendant call button and the electronics that manage the computer processes, making the pod exceptionally safe to use.

      If the pod is insulated and the room is heated correctly then in-line is extremely efficient – our i-sopod automatically monitors the solution and will turn over the water each time there is a drop in temperature to help keep it at a constant temperature rather than heating the water after it’s dropped overnight.

      Our pod automatically filters after each session and sometimes the in-line heater will come on during this process and other times it won’t have too as the temperature during an hour hasn’t significantly dropped.

      Maintenance of a waterbed heater is a nightmare as you have to empty the pod and take the whole tank apart. Waterbed heaters constantly go wrong or lose power. Floatworks who I bought my i-sopod from said they have 100’s of pods in the field and have yet to have one inline heater fail.

      As an owner of a waterbed heated tank and an in-line – I have to say the in-line is the way forward providing the tank is well insulated and the room is keep at a good temperature too.

  2. […] If you would like to read about the difference between inline and waterbed heaters for float tanks, click here. […]

  3. Adam Avatar

    Wow that was a great response to this question. I’m on this forum right now because my samadhi waterbed heater just crapped out on me last night. I’m faced with not too many options and they all aren’t fun
    A new heater liner and clips for the tank which all would need to be replaced in order to fix this problem and recover 50% of my float capacity as we only have two tanks operational. Now only one. Also we just opened two weeks ago. I believe some solution got under the liner and might have attacked the heater causing it to fail.
    We are now having to close the room and work with 1 tank. Not a good scenario. 858 from samadhi for the parts to replace.
    Can I put an inline heater on this current system or should I just sell this tank close up the business and go find a job at Google?

    1. Dylan Schmidt Avatar

      Hi Adam!

      Google is a great company that will provide splendid health benefits, PTO and you even get to spend 10% of your time working on your own projects! … … But my guess is that you didn’t start a float center for the discounted lunch bar. If you are serious about running your business, you are going to need to identify your leak and patch it or replace your liner. You may want to speak with Samadhi to see if they would be willing to take payments. It seems like everyone I know (including us) have had a very difficult opening week/month that really tests your commitment to what you are creating. If you’re serious about this, get a fix as soon as possible to keep your float tanks up time near 100%.

      1. Adam Avatar

        Thanks for responding Dylan. That really helps. And you’re right it is all about the sustained commitment to give this gift that is ultimately keeping us going and bringing value to this area. I’m understanding that These kinds of issues probably won’t ever stop so I keep working through them. Builds character and confidence and humility.
        Everything we go through with these tanks and centers is worth the pleasure and value offered by the experience.

  4. Dan Schmidt Avatar
    Dan Schmidt

    Great article! I’m replacing a burned out waterbed style heater in my Samadhi Tank. Just wondering if you can recommend a brand of in-line heater for this application. Thanks.

      1. Katherine Avatar

        Question: I have a tank and am having to replace the heater which is a waterbed heater. I am being told by people that since watered heaters are not really grounded that getting electrocuted could be an issue. It seems unlikely but does anyone know anything about this

  5. Bruno Avatar

    Dylan,your forum is really great and really helpful. Im getting answer for a lot of my questions and for questions I didnt knew already! thanks a lot. And the comments are great too, so thank guys.
    Im in brazil and Im planning to build my own tank and Im investigating the idea to put and in-line heater and also an underneath one.
    For the underneath tank, did anyone know what is the technology and more details? I saw that in the zen float tent they use like heat pads, like the ones for pets. But I think in other tanks they use a more proper technology. Im new in this research so I don’t know my question is stupid or naive, but I will appreciate some light on this subject.
    Thanks a lot!!!!

  6. Vince Avatar

    So what size inline would be needed to heat a 300 gallon pod in 15 minutes each morning ? My system came with a 1.5 kw which takes 3 hours to bring it from 21c to 34c …thats ridiculous… im thinking of using a 1000 watt immersible fish tank heater during the evening to keep temp and run the pump and inline heater for 15 minutes in the morning before use.. any thoughts ?

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