... 8-10 per hole 3. 15Years Warranty for vacuum tu Non-pressure solar water heaters(ss)1.CE,ISO9001,CCC, 2. ... the use of more safe, non-troubled waters, anti-burst, antifreeze, E-nrichment process.Collector device:φ47×1500,φ58×1800Nano-nuclear ... material: zinc-based anti-corrosion steel plate thickeningWorking pressure: no pressure to runWater method: water law. Non-pressure solar water heaters(ss)