I sat down recently with John Tortorella, a designer and builder of custom gunite pools in Southampton NY, and the CEO and founder of the Tortorella Group, to discuss pool durability and energy efficiency, two qualities that are “top of mind” for the Sunset Green Home project.
If you’ve been following our story, you know that the old house on the site of the Sunset Green Home project was made uninhabitable by Hurricane Sandy. The property didn’t have a swimming pool, but the new Sunset Green Home will have one. So, just as we have been thinking about durability and energy efficiency for the Sunset Green Home itself – which we hope will earn LEED Platinum certification at completion – we are thinking in parallel about the same issues for the swimming pool.
Like many coastal properties, Sunset Green Home will be built on pilings that are approximately 10 feet above current grade. The pool will be set into a deck at the level of the ground floor of the house. On the one hand, this means we won’t have to do any excavation. On the other hand, it also means that the entire pool structure has to be constructed above the ground…which is somewhat complicated.
Our pool construction, just like that of the house, starts with pilings that are driven deep enough into the ground that they can support the load of the pool structure with no movement. The pool contractor will then build steel (rebar) and concrete grade beams that span the piles in order to distribute the pool load over the piling system.
Durability is critical! Think of it this way: at 70 degrees, one gallon of water weighs 8.3 pounds. Multiplying by the volume of the pool, we estimate that the Sunset Green Home pool will hold over 143 TONS of water (we used this pool volume calculator). That’s a lot of weight. And now imagine a similar storm surge to that of Hurricane Sandy, which would send a velocity flow of water right into the vertical wall of the deep end of Sunset Green Home’s pool.
So how does one build a pool to withstand these types of forces? And, if we’re going to be as energy minded about the pool as we are about a home that is seeking LEED Platinum certification, what should we do about energy efficiency? These are the questions Kathryn Cannon (Sunset Green Home’s sustainability consultant) and I posed to Mr. Tortorella.
The first thing he did was pull out his mobile phone and show us a photo of a pool he had built just prior to Hurricane Sandy, which the homeowner's insurance adjuster believes may very well have saved the owners’ oceanfront home. The pool had been built on helical piles just up against a dune. After the storm, when 100 feet of dune had been washed away, what was left was the exposed underside of the pool structure – which was completely undamaged. THAT, John Tortorella said, is a durable pool. And, because the pool withstood and deflected the forces of the storm, the house behind it was undamaged.
So what makes a durable gunite (i.e., pressure sprayed concrete) pool?
- The quality of the rebar used for framing of the grade beams and pool walls. Tortorella uses 1/2” and 5/8" thick rebar (and thicker rebar in some cases) versus the industry standard 3/8” thick steel on even his standard pools, and his crew takes care to bend – not splice – the pieces where angles are required
- The design of the rebar caging for grade beams and pool structure. Depending on how high the pool is built above grade, the rebar structure may vary from a single cage of 1/2" rebar at 10" on center, to as much as a double cage of rebar for a pool that one can literally walk beneath. To avoid cracks, Tortorella reinforces his pool structures with rebar under and around the pool skimmers
- The density of the concrete walls. It’s not enough to specify a particular thickness of gunite. Tortorella nozzlemen receive extensive training and are certified for gunite application, which Tortorella says results in a uniform, dense application that contains no “voids” within it. It’s the uniformity of coverage and proper encapsulation of the steel rebar that gives the gunite its strength
- Sizing the pipes correctly. The durability of the pool pumps and other equipment depends on smooth flow of water through the system. Undersizing the pipes or including too many twists and turns will cause the pump to overwork, resulting in shorter equipment lifetimes and increased - unnecessary - electricity use
- Including pool components that work holistically to deliver a safe and comfortable aquatic environment. Salt water pools are the state of the art, and their salinity is approximately equal to that of a human tear. Such pool chemistry, if properly balanced, will feel better on skin and eyes, and provides for more pleasurable swimming. The salt in the pool is also used to create pure chlorine via a salt generator. But Tortorella warned that the process of generating chlorine from salt will raise a pool's pH - so using a salt generator alone is not recommended. He cited a trio of Pentair products – Intellichem (the "brain" that continuously measures and tests chlorine and pH levels), Intellichlor (which produces chlorine from salt) and IntellipH (which balances the pool's pH level) – that work together to adjust and maintain a pool’s chemical balance. But he warned that using the salt generator alone, which some customers do to control first costs, may be penny wise and pound foolish...doing so may result in rough and unsightly scale buildup on the pool walls and may deteriorate the pool heater's heat exchangers.
And what about energy efficiency? There are things that pool owners can – and should! – do to reduce a pool’s energy use and environmental impact.
- Install an ASTM-approved automatic pool safety cover…and then use it! Not only will this habit result in a safer pool environment, but closing the safety cover when the last swimmer comes out of the pool can save up to 70% in heating costs, and will reduce by as much as 50% a pool’s evaporative water loss and 60% of pool chemical consumption according to the US Department of Energy
- Include an ENERGY STAR certified variable speed pool pump. According to the US EPA’s ENERGY STAR web site, on average such pumps result in savings of over $300 annually (and potentially even more in warm climates where pools are used throughout the year or when the newest and most efficient models are installed; John cited a savings of as much as $1,800 - $2,000 for local installations using the Pentair model). In fact, according to the ENERGY STAR web site, “If all pool pumps sold in the United States were ENERGY STAR certified, we would save about $113 million per year and prevent greenhouse gas emissions equivalent to those from 140,000 cars.”
- As above, design the pool’s plumbing system correctly. An energy efficient pump is no good if it’s trying to push water through a pipe that is too small! Getting the plumbing right means that the pool pump won’t have to work so hard to move the water through the system.
- Heat the pool water using solar panels (which work best during the warm sunny months of the year) instead of gas heaters (which burn fossil fuels and contribute to global warming). And install solar PV panels to generate electricity for supplemental pool heat (check for federal, state and local rebates and tax incentives). Design the pool with “deep heating” – heat rises, so heat the pool from the bottom rather than at the top to avoid losing the pool heat into the air
If you’re building a new swimming pool, make sure to ask your contractor to incorporate these and other best practices into its construction and operation.