How the system works
Florida solar water heating is normally a direct, open system: the household water itself is pumped from the storage tank up through the collectors and back down again. The water in the collectors is the same water that comes out of your tap, so there is nothing separate to service or top up.
A controller with a collector sensor and a tank sensor runs the pump when the roof is warmer than the stored water, and stops it when it is not.
The tank and the backup element
The storage tank holds the hot water and almost always contains an electric backup element with its own thermostat, so you still get hot water on a run of cloudy days.
That backup is also the reason a failed system can go unnoticed for a long time. The pump stops, the collectors stop contributing, the element quietly takes over the entire load, and the only visible symptom is a higher electricity bill. If your bill has crept up and you own solar water heating, that is worth checking.
Temperature and mixing valves
Solar can push stored water considerably hotter than a conventional heater would. A tempering or mixing valve blends it back down before it reaches your taps.
If that valve fails you get one of two symptoms: water that is suddenly far too hot, or water that never gets properly hot even though the tank is. Both are the valve rather than the collectors.
Leaks
- The temperature and pressure relief valve discharging. Sometimes correct behavior, often a sign of a real problem, never something to plug.
- Tank fittings and connections, especially on an older tank.
- Collector plumbing and roof penetrations.
- Anywhere the pipe run passes through the attic, where a slow leak can do a lot of damage before you see it.
Circulation problems
- A failed pump. Often silent, and the easiest thing to confirm on a service visit.
- A failed sensor, which makes the controller run at the wrong times or not at all.
- A stuck check valve, which can allow reverse flow at night and actively cool your tank.
- Air trapped in the system after work or after a drain down.
Freeze protection
Because the collectors hold ordinary water, a hard Florida freeze is a genuine risk. Systems handle it either by recirculating warm water from the tank or by draining down. If the protection fails, collectors and exposed pipe can split, and the damage usually shows up as a leak on the first warm day afterwards.
Before a cold snap, knowing your controller and pump are working is the whole of the preparation.
Scale and ongoing maintenance
Florida water is hard, and it is going through your collectors. Scale builds up over years and slowly reduces performance.
- Anode rod condition, which protects the tank from corrosion.
- Backup element and thermostat.
- Temperature and pressure relief valve.
- Pump, check valve and isolation valves.
- Controller and both sensors.
- Freeze protection function.
- Descaling where performance has dropped off.