It was a hot day today (36 decrees C), and has been quite warm for the last few days. At about 1pm I noticed that the hot water service was boiling.
Normally on a hot day it boils/gurgles a little bit, maybe overflows about half a litre, and that happens throughout the day every 20 mins or so. And thats OK. Thats what its supposed to do – its an open vented system.
Well, today it just continued to boil, like a kettle, non stop. I didnt think that was too good, so the only way I could think to cool it down was to cover the solar evacuated tubes. So I got up on the roof with a canvas tarp, and covered up the tubes. Problem solved.
So, I am thinking that might be a regular occurrence, particularly when we have built the house and are not drawing much water (ie heat energy) from the hot water tank.
Will have to keep an eye on it.