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I recently built a pool and spa in one of the foggiest, coolest environments in California.  This pool, high on a bluff in Elk, is not heated by fossil fuels.  The only source of heat is an array of vacuum tube solar collectors.  I was at the site yesterday.  The pool was 84 and spa 103.  The solar system heats (3) 120 gallon storage tanks which distribute heat to titanium heat exchangers for the pool and spa.  The pool is the heat sink for the system.  A few weeks ago the owner reported that he pool was 95 degrees so he rolled back the auto cover and dumped 14 degrees overnight.  The pool has been in the mid '80s since.

The solar system also heats the residence, a 5000sf custom home with hydronic heating, in the winter.  When the home is up to temperature the excess heat is dumped into the pool and spa.  The residence  is prioritized in the winter with the spa second and excess heat into the pool.  The priorities are set by thermostats.  When the tank reaches 110, the residence heat is turned on.  When it reaches 120, the spa heat is turned on and 130 the pool heat is activated.  It is extremely efficient, even in the fog.  The vacuum in the tubes is a perfect insulator.

There is a Munchkin 110k BTU back-up boiler but we don't anticipate having to use it.

The pool is a custom 2 sided zero edge design with one side a 105' radius.  This required an in-deck cover track on that side with a standard under-coping cover mount on the opposite side.  It covers the overflow troughs on the side and end for additional heat retention.  The spa is a pretty standard 6 jet spa, 6'-10" round.  The custom detail for the spa is the coping.  It was designed and manufactured with a 2" recess to accommodate an aluminum Be-Lite spa cover so that it is flush with the deck.

I got the typical plan view of a shape from the architect, nothing more.   The  owner wanted a vanishing edge pool.  I indicated to him the heat loss on a VE pool and suggested the zero edge design.  I did the design and specifications.  The owner already had a PV solar system and added a little more capacity to handle the pool.  Although the pool pump must stay on all daylight hours, the spa pump cycles with demand to save energy.

Another selling point for this type of solar heating system is that, since it heats the residence, it qualifies for federal and state solar tax credits which saved a substantial amount of the cost of the system.  The solar is utilized year round for optimum performance and savings.  We expect this residence, pool and spa to use no power or fossil fuels.

The solar contractor is Solar Hot Water Plus in Arcata, CA.  They work all over California and can consult, design and install:  www.solarhotwaterplus.com