Natural Swimming Pools

Is there really such thing as a “green” swimming pool?  I’ve been wondering this for about a decade now.  We had planned to build a natural swimming pool(NSP) on our property as soon as our kids could safely swim – and that day has finally come.  We are now in the planning phase and hope to start construction in early spring if all goes well.  There are many types of natural swimming pools and they can be the same style and materials as a conventional swimming pool or look like a natural pond.  So what is a “natural swimming pool”?  It has two main components:
  • the swimming zone – can be made with pond liner or even a gunnite concrete material with tile like a conventional pool.
  • a regeneration zone – where plants rooted in gravel substrates consume the excess nutrients.  This area can be within the pool behind a separation wall, or in a separate vessel altogether.
According to FLL standards, the NSP pool types vary from Type 1 being a single vessel with no plumbing – which is only possible with a large surface area of water- and to Type 5 which is where the two zones are in separate vessels, making it look very similar to a conventional pool.  The difference between type 1-5 is the amount of plumbing involved, which also determines the minimum sizes these pools can be built and the amount of maintenance or costs involved.  The most commonly built NSP is a Type 3 which is built with a similar plumbing design to a nice koi pond.  Infact, our koi pond that our kids occasionally swim in (see  right photo), fits the criteria of a Type 3 NSP – other than we have fish, and that is a no-no for NSP systems.
These systems have been around in Europe since the early 80’s and hundreds have been installed, including large municipality water parks all through Europe.   Here is a short video of an NSP I found on youtube – which has quite a few to browse for inspiration.  This slideshow also has some great photos.

There is a great book we’ve used to study the subject – but not much has been done or documented in the United States 0r North America that I have found.  I would be delighted to find someone local with more experience on the subject because of regional considerations.  We recently attended a workshop with Bionova, but might need an excuse to travel to Europe to see some of these systems in action!
To answer my initial question about being “green”?There are no chemicals required to maintain these NPSs because of the biological filtration systems.  In that regard, a chemical-free pool is great!  From an electrical consumption standpoint, it really depends on which type of system is installed because there can be a complex pump and filtration system used which require a lot of energy to use.  Not to mention a lot of materials are required to build a NSP, gravels, liners (or masonry materials), plumbing, etc and the fact that it will require a lot of water to refill from evaporation (1/4″ per day) all make it a fairly large carbon footprint component to build and operate.  If we could figure out a design with solar panels to run the electrical and rainwater to refill the pool – it would make it more “green”.  But does the non-chemical aspect make up for the carbon footprint just to install it?  Not to mention to price tag – we were told that an approx $100per square foot for install is typical, making the smallest size possible which is around 600 sqft, equaling $60,000 on the low end… and that doesn’t include surrounding landscaping,  permitting etc.
All along I thought these closely mimic natural wetland systems, so it was a big surprise to learn that systems do not include any soil or organic matter for the plant growing media.  It seems to work in the pools which are functioning, but I really would like to know how much plant replacement is happening and how often.  Also, any decomposing materials need to be removed, which makes it high maintenance – in waders!  But that actually sounds like fun!  If we do build one this upcoming spring, I will be sure to post the progress…