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They won't see us waving from such great heights
A question for those of a scientific turn of mind.
I live in Oxford which, as many of you know, is a hard water area. Our kettle needs regular de-scaling, as it quickly fills up with concrete-y white deposits. I'm sure the iron would too, if we ever used it.
Recently, the shower has been communicating to me that it needs de-scaling; it does this by running extremely hot. This isn't as daft as it sounds: scale lowers the water throughput, and thus the shower is heating much less water than it thinks it is, the net result being that it heats it too much (at least, that's my understanding).
It's always a fight to dismantle the showerhead, but when one does the deposits found therein always turn out to be a virulent shade of jade-green. Why ? Is it in fact not scale, but some mysterious by-product of a disintegrating copper water tank ?
And for those who are not of a scientific turn of mind: what do they call cider in America ?
I live in Oxford which, as many of you know, is a hard water area. Our kettle needs regular de-scaling, as it quickly fills up with concrete-y white deposits. I'm sure the iron would too, if we ever used it.
Recently, the shower has been communicating to me that it needs de-scaling; it does this by running extremely hot. This isn't as daft as it sounds: scale lowers the water throughput, and thus the shower is heating much less water than it thinks it is, the net result being that it heats it too much (at least, that's my understanding).
It's always a fight to dismantle the showerhead, but when one does the deposits found therein always turn out to be a virulent shade of jade-green. Why ? Is it in fact not scale, but some mysterious by-product of a disintegrating copper water tank ?
And for those who are not of a scientific turn of mind: what do they call cider in America ?
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-Washer in fitting where shower joins onto water system - is it disintegrating? This is most likely cause
-Copper pipes, especially at fittings - there will be green all over them if one of them is corroding
-Things in guts of shower, possibly.
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I had thought the US called cider applejack, but someone told me that that's actually more like apple brandy.
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Quite a mistake, but hopefully there'll be no harm done.
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apparently limescale increases copper corrosion as it acts like an anode to the coppers cathode, making electolysis take place slowly.
and also some FACTS:
"As the temperature of water increases, the volume of scale it holds in solution drops, resulting in the precipitation of scale molecules into the water. These molecules join into crystals either on rough surfaces or on other crystals. Likewise, as the pH increases or as pressure decreases (as it does when water is flowing along a pipe or through a control), the volume of scale held in solution drops resulting in scale formation."
so warmer water, higher pH, and flowing water increases limescale
still dont understand why the shower runs hotter though.
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Suppose the shower normally heats 1L or water by supplying 1KJ of energy. If the limescale reduces the flow so that only half as much water can pass through during the same time interval that's now 1KJ heating 0.5L of water.
Same amount of heat applied to less water means higher temperature.
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Assuming it's the usual kind of electric shower, they generally have two user controls: one to set the amount of heating (typically 'none, ie cold', 'some' and 'lots'), and one to adjust how fast to let the water out. The slower you let the water out, the longer it spends around the heating elements, so the hotter it ends up. This is why the flow rate control is typically labelled as a temperature control, although this is not what it actually does. So a bunged up shower head has the same effect as turning the flow rate down, and the water's hotter.
I have occasionally seen showers where not only is the flow rate control labelled as a temperature control, but the temperature control is labelled as flow rate...
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Thought that was a bit weird- it's a long time since I've done any chemistry but I remember vaguely that the solubility of anything in anything increases with temperature (summat to do with thermodynamics and entropy I think), and this sounds like it's going the wrong way.
Just had to go look it up and apparently it's more complex than the simple solubility I was expecting- at lower temperatures most of the scale is nicely soluble calcium bicarbonate, but above ~70C it starts decomposing to calcium carbonate (& carbon dioxide & water), and that's a lot less soluble so precipitates out.
Water chemistry always was too complex for its own good...
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