6 Star Hot Water & Plumbing were called to investigate the sound of water trickling down the rain water downpipe. The owner was aware that the water may be coming from the solar hot water system collectors on the roof.
When our plumbers arrived, they found that the auto air bleed valve on the evacuated tube solar hot water collectors was leaking from the vent at the top of the valve.
Why this occured
Auto air bleed valves generally freeze and the outer casing will split during heavy frosts. During summer, the auto air bleed valves can overheat due to extreme temperatures in the collectors. This causes the internal mechanisms to disintegrate or warp out of shape. As water was leaking from the vent at the top of the valve and this occurred during the warmer months, we knew it was heat related.
The solar hot water system was a Kelvinator evacuated tube system. Because Kelvinator systems have a reflector panel behind the glass tubes, they will generate extreme heat in summer.
We turned off the water to the solar hot water system. We removed the old auto air bleed valve and we installed a new valve. If the sun was shining the collectors would generate a lot of heat and would make the system very dangerous to work on. Normally, we would cover the collectors and wear gloves. However, because it was an overcast day we did not need to cover the collectors or wear gloves while we removed the damaged valve.
We insulated the new valve to protect it against extreme cold weather. The only environmentally sustainable solution to the overheating problem on Kelvinator solar hot water systems is to cover a third of the tubes in summer to reduce the surface area exposed to the sun.