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Getting the pool/ spa combo right By Cal Stanley
32 SPLASH! June/July 2020
I
am aware of two instances of a concrete spa constructed as part of a swimming pool that left the spa effectively useless. Why? Because no thought was given to how they could both be used at the same time. Both are in very high-end properties where the cost of installing the pool and spa correctly would not have been an issue. Neither spa had a skimmer box even though it is required by AS2610.2. Spa 1 had air rings around the seat and the floor but no venturi jets. The seat edge in this one was a sharp 900mm with glass tiles. It was hydraulically separated and took at least three hours to heat up and the four suction covers were easily removed, thus breaching AS1926.3. AS2610.2 requires that the water depth in a spa not exceed 1100mm and on a spa seat, 600mm. The footwell of this spa was so deep even the feet of a person six foot or taller could not touch the floor. Spa 2 was not hydraulically separated from the pool, making it almost impossible to heat. Should it actually ever reach spa temperature, the pool will also have increased by about five degrees. It had 10 spa jets installed (several in the seat corners where they could not be used) and water to them was supplied by a 2hp pump via a rather tortuous 50mm pipe which, when it reached the ten 40mm jets, led to not much more than a dribble from each. It did not have a designated spa filter. Remember, it has no skimmer, the water level was above the pool separation wall and the only filtration for the spa was via a single eyeball from the pool’s filtration system. The right way There is really only one way to build a concrete pool/ spa combination and that is to separate them. The spa can even overflow into the pool when not in use. But when it comes to heating and using the spa, it must be hydraulically separated from the pool. The spa can be part of the concrete pool structure. It can be raised above the pool level and when not in use, water from the pool filter can be directed through the spa and overflow back to the pool. However, it is vital that the two water bodies be, or be capable of being, hydraulically separated when it is time to use the spa. This does mean two pumps, two filters, a separate spa jet pump, venturi jets, two chemical control systems and often two heaters. Why is this?
Heating
The owners will likely use the pool more than the spa. They will want the pool heated constantly to a comfortable temperature. If it is indoors or easily covered, the pool heater won’t need to be very large. The spa, on the other hand, needs to be heated as quickly as possible – and at this level of construction in the high-end market, they’ll want it heated in 30 minutes or less. Believe me, no client enjoys having to wait several hours to use their spa! So, I regularly installed two gas heaters with the larger one (about 400 MJ) fitted to the spa. A smaller heater should easily maintain the pool temperature once it has been reached.
Filtration
We all know, or should know, about the “gunk” that comes out of the skin when a group of adults are in a hot spa. This will be a considerable and unpleasant problem if the spa has no skimmer box to constantly remove it. And, who would want it to overflow into the pool!
Blowers
A spa jet should produce a relatively strong water flow that is softened by air entering through the venturi jet. Spa 2 above has insufficient flow to venturi in any air, so the “jet” consists of about 80 per cent air and 20 per cent water. It is very harsh on the back.
In conclusion
Concrete spas are never as comfortable as acrylic ones. So, we in the concrete pool business must make every spa as special as we can. I hope and I’m sure most pool builders would not make as many fundamental errors as in Spa 1 and Spa 2 above. What I suggest will add considerably to the pool/spa cost. However, when explained correctly, I am sure your clients will gladly pay for the best pool/spa combo you can give them. n For these columns, Cal Stanley draws on his experience and success in pool construction, having run award-winning Neptune Pools in Western Australia for three decades, as well as sitting on many standards committees and industry body boards, and working as a pool consultant, trainer and delivering hydraulics courses for the swimming pool industry. If you have a question regarding his columns, email him at neptunepools@westnet.com.au.