My hot water immersion heater has packed up three times in two years. On
two occasions it required a new thermostat; on one it apparently needed a
whole new unit.
Now, I'm not saying I don't trust plumbers :-) but something's wrong
Any suggestions please?
Also - does anybody know of a good site that will walk me through the
process of removal and replacement? At least my own time is free....
I don't know of any sites but: -
Firstly, you need to close off the entry water to the cylinder, then attach
a piece of garden hose pipe to the drain point, which should drain to a
bucket or preferably outdoors. The discharge point of the hose, should be
below the "head height" of the heater screwed connection to the cylinder.
Then; and most important to avoid excess shearing stress on the cylinder
copper, before emptying any water from the cylinder - just loosen the
heater, using a box spanner which can be bought from the sheds or a plumbing
supplier, until there is a slight seepage of water, at the joint between
the heater and the cylinder, Now drain the water to a level to just below
the heater thread, i.e. when the seepage stops. Finally, slowly unscrew and
remove the heater completely.
Follow the manufacturer's instructions for replacing. Ensure that the cable
supplying the heater is of the heat resistant type; and is not brittle or
showing signs of overheating of the cable or the cores. Check the thermostat
setting is still the same and re-install. The drain point should still be
closed off, refill the cylinder by opening the inlet valve and switch
Immersion Heater Element Notes
They all have the same mounting boss, but there are different lengths. The
most common lengths are 11", 18" and 27", but there are also 30" and 36".
You need to get the one that suits your cylinder.
If you have a side entry element, mounted near the base of the cylinder,
then the length is probably 11". If you have a top entry element, then it's
If you have a dual element (top entry only), then you need to replace the
whole assembly - they're a bit more expensive but you have no choice.
BTW, get an Incaloy coated element - they last much longer. Titanium coated
ones even longer.
How hard is the water? That could drastically affect the life of
immersed heaters. As can fitting too long a heater and bending it to fit
in. As can buying cheapest possible imports, rather than quality
products. Do you often change the temperature settings on the
thermostat? Ever drain down the system with the heater still on?
There are many possible reasons for an early failure.
The good news is that, since the units have been replaced recently, the
whole lot shouldn't have had time to corrode and seize solid. So getting
the bits out to replace them shouldn't be too tricky. However, you will
probably need to buy the correct tool to remove the heater.
If you drain the tank down, a dentist mirror and a lamp should allow you
to have a quick look at the condition of the inside of the tank and more
importantly the condition of the central heating heat exchanger coil. If
they look to be in a bad state, now might be a good time to swap out the
entire tank. eg before the rust inhibitor in the central heating loop
starts appearing out of the hot water tap...
On Thu, 17 May 2007 10:31:58 +0000, Palindrome wrote:
Thanks so much for the responses - I followed them slavishly. First I
replaced the thermostat - still no dice. Then I replaced the whole unit -
What I still don't know is why it packed up so quickly - visually, it
looks in perfect nick. Probably got what I paid for...
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