Eco Pool and Natural Spa, One Community Natural Pool

Duplicable City Center Natural Pool & Spa

This page is the open source and free-shared design and construction page for the Duplicable City Center natural indoor/outdoor swimming pool and eco-spa. This page will continue to evolve until it includes complete open source and free-shared county approved comprehensive building plans, purchase orders, construction instructions, editable CAD downloads and Sketchup files, construction tips and tricks, maintenance details, and all other needed specifics for duplication and care of this natural pool and eco-spa as parts of the Duplicable City Center or as stand-alone components.

Duplicable City Center Indoor outdoor pool final render, One Community

The One Community Duplicable City Center | Eco-Pool Concept Render – Indoor View – Click to Visit the Natural Pool Page

After that it will evolve even further through global collaboration and sharing the evolutions and adaptations of other people’s projects using these templates and plans. This page includes the following sections:


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A natural pool is a pool that functions safely without the use of chemicals; in this case, using ozone, germicidal UV, bio filters, and Hayward sand filters utilizing recycled glass to maintain clean and healthy water. An eco-spa is a hot tub designed to function safely with the minimal use of chemicals; in this case using ozone to minimize chlorine use. Some of the key features and intentions for the Duplicable City Center natural pool and eco-spa designs include:

  • County approved plans
  • Powered by 100% off-grid energy
  • Outdoor wading pool lush with plants
  • Central pool with indoor/outdoor swimming access to the Social Dome
  • Verifiably safe water quality with minimal or, in the case of the pool, no chemical use*
  • Ability to completely close the indoor/outdoor transition point for heat retention (see below)
  • Ability to be duplicated independently of the Duplicable City Center and independently of each other
Duplicable City Center natural pool and spa final render

The One Community Duplicable City Center | Eco-Pool Concept Render – Inside Court Looking East

* We will install a chlorine-feeder for emergency situations and will utilize an ORP meter to gauge safety. The chlorine feeder and ORP meter will allow this design to meet code is almost any county. This statement from Del Ozone leads us to believe chlorine will never be needed: “The Solar Eclipse uses DEL’s proprietary Plasma Gap Ozone Technology (patent pending) combined with high output, low-pressure germicidal UV lamps to make a potent yet economical AOP system small enough for residential pools. This system takes advantage of one of the chemical reactions that create an Advanced Oxidation Process: ozone irradiated by UV light in the 254 nanometer wavelength produces hydroxyl free radicals”

Natural Pool, Eco Hot Tub, One Community

Natural Pool and Eco Hot Tub Layout – Click to Enlarge

Duplicable City Center Indoor outdoor pool final render, One Community

The One Community Duplicable City Center | Eco-Pool Concept Render – Indoor View

City Center Indoor Outdoor Pool Central View Looking Northwest final render, One Community

The One Community Duplicable City Center | Eco-Pool Concept Render – Inside Court Looking Northwest


The One Community Duplicable City Center | Eco-Pool Concept Render – Outside View Looking Northeast



Duplicable City Center Natural Pool and SpaWe want to inspire more people to build natural swimming pools and eco hot tubs. We’re doing this because it supports healthier people and a healthier planet and we know that open source sharing these designs, the permitting process, the building process, the safety-testing process, maintenance, and all the specific benefits of a pool and hot tub like this will hold huge value to a broad diversity of people. Additionally, we know if we make these designs easy enough, attractive enough, and provide enough of the foundations to also make them affordable enough, then the other benefits will promote themselves and help more and more people to start investing in this more sustainable option. As part of One Community’s global-change methodology, we see this as having the potential to produce an entirely new mainstream interest in these kinds of designs and all the benefits they provide, growing and promoting the entire industry and all people and businesses associated with it.

Duplicable City Center Natural Pool, Outside View Looking Down

The One Community Duplicable City Center | Eco-Pool Concept Render – Outside View Looking Down





Da Ku: Mechanical Engineer
Jennifer Engelmeier
: Eco-pool and Spa Equipment Specialist
Meg West: Landscape Architect, Permaculturalist, and founder of Meg West Design
Rick Ruggles: Swimming Pool Equipment and Health Consultant with Hayward Pool Products
Rob Gjerde: Swimming Pool Design & Construction Expert and owner of Sorico Design and Consulting



Here is the plumbing layout and plan for the natural pool. They include optional solar collectors for passive water heating assistance, natural filtration, backup chemical sterilization, and pump system with a heater bypass valve that will allow for bypassing the outdoor sections of the pool for winter energy savings:

final schematics for the open source indoor outdoor natural-pool , One Community

Plumbing schematics for the open source indoor / outdoor natural-pool – click to enlarge


Here is the plumbing layout and plan for the eco spa that includes sharing a heater with the pool and optional solar collectors for passive water heating assistance:

Eco-spa design schematic, One Community

Plumbing schematics for the open source eco-spa – click to enlarge



Purchasing details for all components are being assembled now. Here begins the list of equipment we are specifying for what we believe will be the safest, most eco-friendly pool on the planet. Also, with this pool and associated equipment package purposed to meet code anywhere in the US for this particular size pool and spa, The equipment that’s being recommended can also be easily scaled up or down depending on the actual pool size.

This is what the equipment listed here is sized for:

  • Pool size estimate: 16,757 gallons
  • Spa size estimate: 1,500 gallons

Here are the equipment specifics that have been selected thus far – rationale for selection is below:

  1. DEL AOP 50 (Previously known as Solar Eclipse) In-ground Swimming Pool Ozone and UV Generator
  2. DEL Ozone 25 (Previously known as Eclipse 1) and 9-0210-11 Install Kit
  3. Hayward EcoStar SP3400VSP SVRS Variable Speed Pump
  4. Hayward Commercial Sand Filter HCF363T(F)
  5. Zeobrite Sand Alternative Media (made with Zeolite)
  6. Hayward CAT 4000 Automated Chemical Feeder (WI-FI)
  7. Hayward CrystaLogic LED Light for Spa (including Niche)
  8. Hayward CrystaLogic LED Light for Pool (including Niche and 300W Transformer)
  9. Hayward Automatic Skimmers for Pools and Spas
  10. Hayward Low Velocity Square Drain Covers (Suction Outlets)

It should be noted that the idea of a truly chemical free pool, that gets used regularly and is permitted in a commercial environment, is not a complete reality with the technology that exists today. Code in most areas requires adequate sanitization as well as backup sanitization. UV/Ozone and Ionization are good “alternative” sanitizers, although not without their own health concerns and controversy. But neither have a significant residual effect (ionization has a slight residual effect, but it takes so long to kill microorganisms that disease can easily spread). Chlorine, with all its controversy, is still the best sanitizer for killing microorganisms in the pool because it is both fast acting and has residual effects. 

So our goal is to make this a potentially chemically free pool by connecting the chemical controllers, listed below, to the UV/Ozone/Ionizer as the primary sanitizer. The chemical controller would only inject small amounts of heavily diluted chlorine as a secondary backup safety system when contaminates enter the water that the “alternative” sanitizing unit can’t handle in a timely fashion. This way we will:

  • Absolutely minimize the use of chlorine
  • Keep the pool up to code, healthy and safe to swim in
  • Collect and share objective data on exactly how many chemicals we are able to eliminate and how natural an eco-code-compliant commercial pool can actually be

Also, the chemical control unit will constantly measure the pH, and adjust it down to our set point using, ideally, a liquid acid feed pump and tank, with heavily diluted muriatic acid. There are several reason why these chemicals are important in adjusting and stabilizing pH. First is the pH of a human eye is about 7.4, eye drops are usually about 7.5, and anything above or below will likely result in eye irritation. Second, even though the plan will be to not use much chlorine, it is pH dependent, and the closer to neutral the more effective it becomes by significant logarithmic jumps, so if we make what little chlorine we use more effective we will use much less. Plus, what little chlorine that does get introduced into the pool will have a short half-life with the UV generator and the sun.

With all this in mind, here are more specifics on the best equipment set we’ve come up with to balance energy efficiency, effectiveness, safety, ease of maintenance, and chemical consumption:


Here are the pump selections and capabilities:

Pool: Hayward EcoStar SP3400VSP SVRS Variable Speed Pump – EcoStarC variable speed pump with built-in SVRS – 3 years parts & labor

Assuming that the plumbing is hydraulically efficient, and that there is 40’ of TDH or less ( TDH is the total dynamic head – the total equivalent height that a fluid is to be pumped, taking into account friction losses in the pipe), this pump can be set to operate at 2000 RPM’s (60%) (approx. 48 GPM) and would turn this size pool over 4 times per day and consume 343 watts/hour.

Spa: Hayward EcoStar SP3400VSP SVRS Variable Speed Pump – EcoStarC variable speed pump with built-in SVRS – 3 years parts & labor

Assuming that the plumbing is hydraulically efficient, and that there is 40’ of TDH or less, this pump can be set to operate at 3000 RPM’s (87%) (approx. 130 GPM) and would turn this size spa over 100 times per day and consume 1,545 watts/hour.

To meet code, the spa will need to turn over at least 48 times per day, which means that the speed could be turned down considerably, which would consume less energy, and the speeds can be increased with 4 programmable speed options. However, these speed buttons are rarely used in most commercial setting because to change the speeds requires one to enter a password every time. This would be acceptable in a community setting such as ours though, as long as everyone agreed not to change any programming with the password.


The same filter will go on each body of water.

Hayward Commercial Sand Filter HCF363T(F) – 36”, 1,050 lb., 36-144 GPM – 5 years parts & labor

This is a sand filter, but we’ll replace the sand with a Zeobrite Sand Alternative. The filtration rate of this sand alternative raises to approximately 3 microns, where sand only filters down to between 20-40 microns. Here’s an overview of the eco-benefits of this choice:

  • Best filtration (down to 3 microns) giving incredible water clarity
  • 50% lighter to ship, saving fuel and shipping costs
  • After use, sprinkle Zeobrite around your yard as fertilizer (not the edible plants!)
  • Zeobrite lasts as long as sand, which is approximately five years
  • Commercial Pools benefit from Zeobrite in pool water clarity, reduced backwashing, reduced chemical demand and need to superchlorinate

The only drawback of Zeobrite, is that backwashing periodically is required and this adds to water consumption.


Depending on needs, options, and money, the following units will work for each body of water. All of the following control primary and secondary sanitization systems as well as pH. All of the CAT controllers include a 5-year limited warranty on controller and 2-year on the sensors. The HCC controller has a 1 yr. warranty on controller with factory labor.

Hayward CAT 4000 Automated Chemical Feeder (WI-FI) – Communicates anywhere in the world via Wi-Fi. Remotely control and view water chemistry through apps or web, receive alarms indicating problems. Web-based management requires monthly subscription

The primary sanitizer we’re looking at for each body of water is from Cambell Environmental Systems

  • 10-year warranty
  • NSF approved
  • Multi stage unit alternates between UV and copper/silver ionization. 
  • With the secondary chlorine tank, one chemical controller listed above would be effectively using three different and effective methods of sanitization.

Two Stenner tanks, with attached chemical feed pumps, for each body of water. One housing diluted liquid chlorine and the other diluted liquid acid. 1 year warranty on tanks and chemical pumps

  • Diluted liquid chlorine is used as secondary sanitization system

Solar Breeze robotic surface cleaner

  • Continuously skims the surface all day and into the night, when able to catch some solar rays.
  • Uses zero electricity
  • Has a 50 micron filter that is constantly filtering the dirtiest water in the pool, which is on the surface.
  • Able to catch a greater volume of large debris that most skimmers

Note: Not normally recommended for a commercial pool because it would get stolen

Tiger Shark Plus RC9955 robotic cleaner

  • Ease of maintenance. Put it in for a couple of hours when needed, or on a regulate schedule, plug it in and walk away. It will clean the entire surface of the pool including steps and tile, and it has a beach entry sensor.
  • This size pool would take about 1.5 hours
  • Built in filter down to 5 microns, with a filtration rate of 75 GPM
  • Outside of the solar cleaner listed above, this is the most energy efficient form of automatic cleaning (Transforms 120v to low voltage)
  • Comes with remote control for spot cleaning

POOL: Hayward CrystaLogic LED Light for Pool (including Niche and 300W Transformer)

  • LSLUS11(030), (050), (100), (150) (cord length)
  • Extremely energy efficient and bright
  • LED bulbs will last 10’s of thousands of hours.
  • Can be installed as little as four inches below water
  • UL listed, low profile all plastic niche (LFGUY1000) requires no grounding or bonding, and the niche gets tied to the rebar so no light box is made of gunite. This saves considerable money over any other lights because it uses less materials such as copper wire for grounding and bonding and gunite for the light box. And saves time, which is money, in the installation process.

SPA: Hayward CrystaLogic LED Light for Spa (including Niche)

  • LPLUS11(030), (050), (100), (150) (cord length)
  • Everything is the same as the pool light except the niche (LGGUY1000) is regular size and requires a light box, however it is still all plastic and does not require bonding or grounding.


  • LTBUY1130, 300W transformer

Accent lights: 12v LED, 320 lumens

  • Small lights designed to accentuate areas in and out of the pool. Fit in 1.5” threaded fitting
  • LAWUS11(030), (050), (100), (150) (cord length)


  • SP10712(S) one each for pool and spa


  • WG1032LV2PAK2 –pool 9” X 9” – comes in pack of 2
  • WG1054AVPAK2 – spa 8” dia – comes in pack of 2

Spa Jets:

  • SP1434PAKA – need 5-6 – it is less expensive and conserves more energy if the air being injected to the jets are plumbed for venturi rather than adding an electric blower

Pool inlet fittings: 4-5 return inlets from the following 2 models specifically designed for low-flow pools to dramatically improve circulation

  • Infusion VRFTH – added benefit of keeping the water warmer – drawback of protruding further into the pool
  • Ijet 004-252-3070-01 – lower profile in wall, color options – drawback is needs to be replaced about every 5 years

Spa heat:

  • Solar heat panels in combination with Aqua Solar control ASC-2P-A-LV
    • Includes 2”/2.5” 3-way valve with GVA-24 valve actuator and 2 sensors
  • Solar is not looking like it will be an option due to the location of the spa, and even if it were, it wouldn’t be enough to heat the spa year-round, so a secondary heat source will be needed:
    • HP21104TC heat pump 110K BTU, works in low ambient operation – still, depending on the climate, in may not work year round
    • If gas or propane turn out to be the most viable option:
      • The only difference between a 250K BTU and 400K BTU is that the larger unit will heat the water faster from cold to ready, but if the spa is being kept at a constant temperature then the BTU size difference for a small body of water becomes mute, with the exception of price. Both will use the same amount of fuel to maintain the spas temperature.
      • H250FD(NA) or (PA)ASME


  • Water conservation is as important as energy conservation. For this reason, and ease of maintenance, the current plan is for automatic safety covers for both the indoor pool components and the spa. The benefit will be lowered evaporation rates, less heat loss due to evaporation, less heat loss due to convection, and less debris and contaminates entering the pool during off-use time. The cover rails can be hidden under the deck so the pool/spa will still have that natural look.



As shown above, the actual swimming pool is an indoor/outdoor pool. Below are two the design plans for the transition point.



Here is a design plan for a door structured to be able to be closed anytime it would be beneficial. Examples of when this might be desirable would be insulation in the winter, sound control when events are being hosted inside or outside, and separation of the swimming areas whenever needed. Da Ku‘s heat loss calculations for this design in a worst case scenario (subzero outdoor temperatures) is around 325W, which is the energy lost per second, for a total evening energy heat loss of around 4kWh, or 0.014 MMBtu.

Door, Frame, Door & Frame – Click to Enlarge

Door - Click to EnlargeFrame - Click to EnlargeDoor and Frame - Click to Enlarge


Cost Analysis:

  1. Plexiglass doors: $522
  2. Gasket: $99
  3. Hinges: $106

The price for a 0.5” thick, 35” * 75” plexiglass is around $261, we need two of them, so $522 (source). The gasket we’d need is around 740 inches, so total cost is around $99 (source). Continuous hinges cost $26.50 each and we need 4 for a total of $106 (source).



Transition design #2 is two underwater openings, one for movement out of the building and one for movement into the building. This is what we are planning now because of its benefits for the City Center HVAC design. By using two below-water openings through the 6″-thick wall instead of a door, we’ll be able to eliminate the “constant open window” affect that the door would create whenever it isn’t seasonally closed. An opening like this will still be able to be sealed in the winter months while providing much better insulation efficiency during the rest of the year. Two openings will also be safer than one by having a separate opening for movement in each direction.

Design details are coming….



Approximate energy consumption for this pool, designed splitting the pool at the indoor/outdoor transition point so we can close that transition point in the winter and still keep the pool healthy and beautiful. This requires double the equipment for the pool. Also, some health departments will require an actual presence of chlorine, some will make exceptions, and some realize that ORP is a true measurement of water quality and safety. For this reason, we’ll have the ability to add chlorine to make them happy while removing it whenever our ongoing pool water testing shows it’s not needed.  

3 EcoStars variable speed pump (2 – pool, 1 – spa)
Max energy draw (100%, 3450 RPM’s) 2,326 WATTs per pump 

Estimated pump use: 

  • 2 EcoStars on pool (2000 RPM’s) – approximately 477 WATTs each
  • 1 EcoStar on spa (3000 RPM’s) – approximately 1,545 WATTs 


3 – CAT 4000’s (15AMP, 120 VAC) approximately 1,800 WATTs (when/if all chemical pumps are operating 


2 – Universal Crystal Logic pool lights (14v, 5amp) – approximately 70 WATTs
1 – Universal Crystal Logic spa light (14v, 2.5amp) – approximately 35 WATTs 

Solar Controller: (120/240v) – (periodic use with solar demand)
Valve Actuator (24v, 0.75amp) – approximately 18 WATTs (periodic use with solar demand) 



Here is a list of water purifying plants under consideration for growing in these natural pools. This list is from the book Growing Clean Water by Bill and John Wolverton and purposed for the most extreme water purification situations:

  1. Water hyacinth (Eichhornia crassipes) “the most effective plant and easy to grow – prolific”
  2. Kudzu (a prolific growing plant)
  3. Sorghum (uptake of contaminants goes into tops of plant mostly)
  4. Tomato (uptake of contaminants goes into the leaves mostly)
  5. Duckweed (Lemmna, Spirodela and Wolffia sp.)
  6. Alligator weeds (Alternanthera philoxeroides)
  7. Arrow arum (Peltandra virginica)
  8. Arrowhead (duck potato) showy white flowers
  9. Giant bulrush (Scirpus californicus)
  10. Soft-stem bulrush (Scirpus validus)
  11. Calla lily (Zantedeschia aethiopica)
  12. Canna lily (Canna sp.)
  13. Cattail (Tipha sp.)
  14. Elephant ear (Colocasia esculenta)
  15. Ginger lily (Hedychium coronarium)
  16. Maidencane (Panicum hemitomon)
  17. Pickleweed (Pontederia cordata)
  18. Common Reed (Phragmites communis)
  19. Soft rush (Juncus effusus)
  20. Torpedo grass (Panicum repens)
  21. Water canna (Thalia dealbata)
  22. Water iris (Iris pseudacorus)
  23. Water pennywort (Hydrocotyle umbellata)

In the book it is suggest to feed the plants to keep them producing. When a plant is full of contaminants (we’re not yet clear on how the average person would be able to determine this), disposal and replacement of the plant is suggested through composting (for non-food use) or burning.



This section will also continue to expand and eventually include complete permitted plans, downloadable 3-D Sketchup and CAD files, instructional videos covering the entire building process, complete maintenance and upkeep details and instructions, and more. Visit our Helping Page for details on how anyone can assist us in making all of this happen faster.





Duplicable City Center Natural Pool and SpaNatural swimming pools and eco hot tubs provide a healthier and more sustainable pool and hot tub environment. This page is the process of open source sharing a chemical-free pool and minimal-chemical hot tub complete with designs and plans, the permitting process, the building process, the safety-testing process, maintenance, and all the specific benefits. We are doing this as part of One Community’s global-change methodology to inspire a new generation of people to build like this and experience all the benefits for themselves and the planet so we can significantly support, forward, and accelerate the mainstream interest, implementation, and further development of these technologies.


The One Community Duplicable City Center | Eco-Pool Concept Render – Outside View Looking Southeast



Q: Has a truly natural commercial pool ever been built in the US?

Yes! Here it is and it is beautiful! Check it out: Webber Park Natural Swimming Pool

If you have a question you’d like answered here, please contact us so we can add it and make this page better.


One Community