I have now had solar water heating for about 4 years and apart from the miserable summer in 2007 am still very happy with it, even more so as the cost of fuel – in my case oil – keeps on going up!
As with each year I have switched off the oil water heating in about May and don’t usually switch back on till early October, so I get about 5 to 6 months of free water heating.
But, recently I was concerned that we didn’t seem to get as fast a heating as in the first year, this seemed to degrade very marginally each year. The solar water heating system was exactly as normal, the pressure was good and there was no apparent change to anything.
What had been on my mind was the fact that we are in a hard water area and when I took the old hot water cylinder out it was about 1/4 full of scale. What with the solar water heating coil being at the very base of the new cylinder, any build up of scale would fall on to that, also the solar heating is set to be higher than the oil heating so that whenever the sun has done its job, the thermostat on the oil system will keep the oil heating off (during April and October ish).
With this in mind I have installed a water softener, about £400 and connected only to the inlet to the hot water system, ie it is on the pipe that feeds the hot water header tank. There have been fairly quick results, the water does seem to be hotter and heats up quicker.
Also there are all the advantages of softened water, we can use less washing powder, scale shouldn’t be a problem, apart from the kettle. My one concern is the impact of softened water on the garden. All the old bath water is used either to flush toilets or water the garden, so as to the long term impact of softened water on the garden, that is yet to be seen, I am told the amount of salt is so very low that it will not have an effect.
Obviously, anybody in a soft water area will not experience the scaling up problems, I would recommend that depending on the hardness of the mainswater, if you are installing what has to be a relatively high cost solar water heating system, certainly consider installing a water softener at the same time. Whatever, if you are fitting a new hot water cylinder and scrapping the old one, cut it in half and have a look – if its is full of scale like mine was (after not that many years), it will give a far more powerful message than simple numbers on a report saying how hard your water is.