charlotte77,
"Can I add a second element to my hot water tank?" NO Unless it has a boss already fitted which is unused.
Try replacing the existing element with a longer one.
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charlotte77,
Immersion heater elements come in a number of lengths, the ones you will usually find are 11, 27 and 36 inches. The 11 is usually fitted in horizontal bosses on the cylinder; you will have to measure the height of your cylinder (flange to base) if you have vertical mounted heater an take off 6" to determine the maximum length of heater that can be fitted.
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