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Old 07-08-2012, 09:04 PM   #1
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Building a Hot Tub and a Swim SPA

I'm planning to build a hot tub (AKA jacuzzi/spa) and a swim spa (two separate structures close to each other)

The basic structures would be made of concrete (4 or 5" thick) with tiles over it. In the hot tub I'm planning to put floor/wall heating (

I would like to purchase a 5HP pump
I would use the same pump for both structures with simple valves switching over between the hot tub and swim spa (perhaps the valves could be used in a way to distribute the pumping action between the swim spa and the hot tub)
I would put 20-25 powerful jets in the hot tub.

I have never built something like this before, therefore I thought I might ask your opinion about some of my concerns:
  1. How do the swim spas create a consistent, turbulence free current (I don't want just one or two jets pumping uncontrolled crazy beams). This is a great concern of mine, and this knowledge is a prerequisit of starting to build the swim spa.
  2. Is the heated wall/floor is a good idea with the hot tub? Should I put some special insulation to prevent heat loss through the concrete?
  3. I have a 30AMP dryer wiring (not used) close to the location where I'm planning to place the pump. Can I use this wiring to power up the pump?
Thank you


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Old 07-09-2012, 04:39 AM   #2
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No pun intended but I think you are in way over your head here. You cannot tile to concrete and expect much and you do not buy spa parts at a box store. You should talk with a pool and spa company before you set yourself up for electrocution or worse.

If you are talking about building one of the short continuous flow exercise pools know that they have a lot of complex systems at work. They are really great for exercise but are not DIY projects.

You might also want to explore the trend toward natural pools.

You need to consider all sorts of things like water flow, spa jets, water heating, filtration, skimmers, safe lighting, and so forth.


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Old 07-09-2012, 07:40 AM   #3
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where do you live? I have an endless pool I'm thinking of selling.
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Old 07-09-2012, 09:05 AM   #4
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I live in Toronto, Canada.

I was checking out the spa companies, but they are very expensive.

I read through these books about spas:
The ultimate guide to spas and hot tubs by Terry Tamminen.
Spas: planning, selecting & installing by Mitzi McCarthy.

I'm quite confident that concrete & tiles are compatible and they are going to last if installed properly (old Roman baths are made of similar materials).

My biggest concern is only the current for the swim spa. How to transform a wild hydrojet power to a consistent current. I was thinking to create a manifold at the water output, but maybe some more advanced physics of fluids is necessary. A schematics or some pictures from an existing pro swim spa current generator would be really helpful.
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Old 07-10-2012, 11:21 AM   #5
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This is not a DIY project.

I have 20+ years in the hot tub business and I would not attempt this project without hiring help. I have seen dozens of pools and tubs that were eventually filled in due to major structural issues or code violations that were impractical to make compliant. Most of these were built by 'professionals' although unlicensed or incompetent contractors are often part of the problem.

Here in the U.S. you would need several special permits to build any structure that amounts to a small swimming pool. You are digging a hole, lining it with concrete, filling it with water, connecting it to electricity and then jumping in the water. You really want to get the water + electricity part right before you stick your toe in the water.

The project would require several inspections along the way such as ensuring the rebar structure is properly grounded and bonded before pouring the concrete.

It might also require health department inspection to ensure the water turnover rate is sufficient and will definitely need an electrical inspection to ensure everything in or even near the bodies of water is properly wired and grounded.

The in-floor heater you propose will not work. Most in-ground tubs use gas heaters but in-ground tubs that use electric heaters typically use at least a 11,500 Watt heater. The in-floor heater you propose only generates 293 Watts.

Nearly all electric hot tub heaters use an element in direct contact with the water (like the water heater in a house) for maximum heating efficiency. Heating the floor will also heat the ground underneath and the Earth is the biggest heat-sink on the planet Any in-floor heating system (no matter how many watts) will be highly inefficient.

Nothing in the description of your proposed floor heater suggests it is safe for your intended use. It would need to be CSA approved for use in a potentially wet environment. Concrete is porous to begin with and small cracks are inevitable which is why even the rebar is inspected for proper grounding and bonding before pouring concrete. Keep in mind the rebar should never carry current and your in-floor heater does.

Your 30 Amp breaker will most likely be inadequate. The pump you propose using draws 16.4 Amps on high speed. A typical 5.5 kW heater pulls 20 Amps. Even most self-contained, 'portable' tubs these days require 40, 50 or 60 Amps to operate and most of these tubs are 8' x 8' and fully insulated.

I could write several pages on why building your own swim spa is a bad idea but will summarize with this: Several manufacturers of portable spas have offered 'swim spas' over the years. Some of these 'swim spas' have had totally inadequate performance and these companies (theoretically) hired hydraulic engineers to design the systems. I personally know of several lawsuits filed over inadequate swim spa performance.

You definitely get an "A" for ambition but I think you'll be much better off looking on craigslist for used, portable hot tubs. There is no shortage of them for sale in this economy (even swim spas) and a used tub will give you plenty of DIY time.

Tom Davis
Bonita, CA
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Old 07-11-2012, 08:11 AM   #6
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Well put, thoughtful, and comprehensive post. You may have just saved somebody thousands of dollars and hours of grief.
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Old 01-17-2013, 04:52 AM   #7
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endless pools? I've seen them in gyms but didn't know what they're called. Is it one of the whole pools or do you have one of the units you fit into an existing pool? Obviously the whole ones aren't suitable for a DIY project but would you be able to fit one of the machines by yourself?
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Old 01-17-2013, 08:34 AM   #8
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As having been a compettitive swimmer from early grade school up thu college and a little beyond, all i can say on this is you do not spa temp water to swim "laps" in. it is either one or the other as far as spa or endless pool.

As Tom Davis indivated in his post there is more to the pool than meets the eye. While concrete and tile do mix, neither are waterproof. concrete pools use a special mix that is "shot" to form the whalls and floor and after that a special plaster coat is applied to waterproof it. He prety much covered all of the bases in his post so I will not elaborate too much on them.
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Old 01-17-2013, 10:54 AM   #9
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shotcrete's just 1 method of forming pools & conc is wtrproof IF the mix design is correct,,, we blt our own w/60a svce & gas heater,,, just search ' ferrocement ' but have 35yrs conc repair/placing/finishing/paving experience,,, pump & htr was sized & bought from local pool/spa store,,, plumbing, structure, steel, & plaster byme, & permit/power by lic electrician

Last edited by stadry; 01-17-2013 at 12:27 PM.
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Old 01-28-2013, 08:05 AM   #10
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SZM How did you make out with the spa? Did you built on, I am interested in putting one in an existing inground swimming pool.


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hot tub swim spa jacuzzi

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