We’ve bitten the bullet and decided to go ahead with the solar panel. It should be up by the end of next week. I’ve also requested a special controller that lets me keep a log of how well the panel is working. We’re not really going to find out over the autumn and winter, although it will make some difference to our gas usage.
In going ahead, I’ve learned that showers are much more complicated than they look.
Currently, we have a simple electric shower. Cold water at mains pressure goes into a little white box and comes out hot.
But with a solar panel heating our water it makes sense to have a shower fed by the hot water tank. This means more options than I’d ever thought about before.
We could have a pressurised hot water system, with the hot water tank at the same pressure as the cold mains. This would mean that the hot water tank could heat the water over 100 deg C – getting the maximum possible out of the solar panel. But the setup costs are much more expensive, so this gets ruled out.
Which leaves us with a gravity fed hot water tank, with a header tank relocated to the attic to give some pressure, but not as much as mains pressure. You can’t mix mains pressure cold water with a lower pressure hot water system, so some sort of clever has to go on in the bathroom.
You could have a separate cold water feed in the bathroom, also fed from a header tank. But this means an extra run of piping.
You could put a pump on the hot water system to bring up the hot water system to the same pressure as the cold water system. I was a bit worried about this option because it seems to me that it might be a way of using the water up quicker, and emptying all the hot out of the tank.
The last – and simplest – solution is to put a pressure limiting valve on the cold water feed to take it down to the pressure of the hot water. I think this is what we’ll be doing.