It looks like the filament in my electric water heater has gone - it must be
20 to 25 years old. Electricity is getting to the switch but, for some
reason, this morning the water was cold and attempts to heat it up now have
Is this something I can change myself? I assume it is just a job of
unscrewing the filament - a tad rustry where it connects to the copper
boiler - and fitting a new one? Of course, ensuring the electrical supply is
switched off when I do this?
Where can I buy one of these - B&Q or do I need to go somewhere special? Is
filament the right word? Is there any specific size or power that I need to
bear in mind?
One last point - it looks like it needs a big wrench/spanner? Bigger than
any I have - is there a special kind I need? Can someone recommend one?
On Sat, 11 Mar 2006 13:02:28 +0000, John Smith wrote:
Could be the thermostat - worth checking - but more likely to be the
Immersion heater is the word (and it goes in a 'hot water cylinder', not
'boiler'). You'll need the same length (usually 27" for top mounted,
11" for side-mounted). There's a grade more suitable for use in hard water
areas if you're in one. The element usually comes with a new thermostat
but if it doesn't buy a new one (of the right length) too as they now have
a separate safety cut-out in case the main thermostat fails to 'on'.
(Check that what you're buying has this separate cut-out just in case
there's old stock still kicking around.) B&Q and other sheds, real
plumbers merchants and electrical wholesalers and retailers should have
I'dbuy a length of new cable too: the old one is liable to be in poor
condition due to heat and age. You want 2.5mm^2 heat-resistant cable and
this may be hard to find except in a proper sparks' merchants.
Yes you'll need a suitable spanner: they tend to be pressed steel and
reasonably cheap. I've seen designs that are (a) flat (b) cranked and (c)
box-spanner with a flat handle off the side. The box and, to a lesser
extent, cranked types allow access when the element is recessed in a
cut-out in a foam-lagged cylinder, but if there's room to use a flat
type I'd get that. You'll need to remove the cable first to get the
spanner on. The immersion element nut will be well stuck on to the
cylinder: don't try to turn it smoothly but instead keep hitting the end
of the spanner moderately hard with a normal hammer until it starts to
shift. (This is why you want a flat spanner: it's a pain trying to do this
with an offset type.)
Clean up the surface off the cylinder boss before
fitting the new element. It may be easier to attach the (new) cable to the
terminals of the element before fitting it, but don't clamp it into the
cable clamp or you won't be able to get the spanner over it. The new
element should have a fibre washer to seal agains the boss but I usually
squish some Boss Green (not Boss White) on to help seal the join. Again,
tap it back using a hammer on the spanner.
John, thanks very much for taking the time to answer in detail.
My Mum passed away 2 weeks ago after 12 weeks in the local ICU and I am
pretty numb at the moment. The last thing I need now - although this is
nothing compared to the loss of my Mum obviously - is extra hassle of this
nature so your information is much appreciated.
Only this morning I was wondering whether I sell or stay but I think my Mum
is trying to tell me something - get a new immersion heater!
Yes unfortunately theres no respite from these things, even when you
least need them.
I almost certainly dont need to say this, but I cant help thinking
theres just that remote possibility: if you unscrew that element theres
gonne be a whole lotta water gushing out. Copper tanks can buckle
during element unscrewing, so it should be loosened a little while
full, then emptied then unscrewed. I would use a fair bit less force to
do it up than it took to unscrew, or it'll never come out again.
Re the house decision, hopefully you've got some time to think it all
through and decide. Selling and buying is a lot of hassle and cost. And
if you take your time then do decide to sell, value will have gone up
due to price rises, and due to you sorting a few bits and pieces out.
I dont envy you.
I was wondering if someone would say that the tank needs to be
emptied before the element is removed.
Emptying is not a trivial matter, unless you have a tap somewhere
that is below the level of the element.
My plumber has installed my cylinder without any means of
draining it. He said that it's easy enough to unscrew the inlet
pipes and attach a hose. Doesn't sound that easy to me.
Once I turned off someone else's inlet tap, and it had not been
turned off for 20 years so it wouldn't go on again. So it pays to
turn taps off and on every few years.
Well, I changed the immersion heater with a new one today and it still would
not heat. I then changed the cable to the spec that you suggested and it
still does not work so now I am assuming it is the electrical timer switch.
I had assumed it was not the timer as when I switch it on to manual a red
'output' switch lights up and I had assumed that power was coming through it
When I turn the mains off this red light remains off no matter what I do
with the timer... so off to be B&Q in the morning for a new timer switch.
Power is obviously getting to the switch as there would be no way of getting
the red light on and I have checked all the connectors/wires coming from it
to the immersion heater and they are connected up fine...
So it looks like the timer swtich is bust? Or am I missing something?
What about the thermostat?
I assume this is the normal sort of immersion heater that screws into
the cylinder. The thermostat (on all the ones I've seen, anyway) slides
down the middle of a tube in the heater, and is connected into the
a) Did you change the thermostat too?
b) [wild thought, please don't be insulted] Did you change the
thermostat, thinking it was the heater?
The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
No, not insulted - grateful for the help.
I bought a complete unit from B&Q which was identical to the one I removed.
It has the element that heats up and goes into the water itself, then the
screw bit that completes the seal part of which, on top, is the thermostat.
The new one has a safety feature if it overheats by which a button springs
up on the thermostat but this is depressed - I thought that might have been
the problem but appears not.
I just don't like using them. Yes, I know how to use them but I still have
an aversion in poking bits of pointy metal in live electrical things.
It was the timer - power was getting to it and the output light to the
boiler was indicating things were OK but they weren't. Yes, a multimeter
would have spotted this but, heck, I would have had to buy one and I just
don't like them. Fitted a new timer and I immediately could hear the
thermostat coming on.
Oh well, still cheaper than calling out a spark... which would have been my
next action relucantly.
I replaced my element - 27 inch for 27 inch a few weeks back - and now I
can't get a decent hot bath from it.
There is a thermostat on it that starts at 50 degrees goes through 60. 70
and 80 and apparently pops out if the water gets as hot as one of the
settings. I have mine set on the 80 degree setting - it has never popped out
once - but my baths are now ruddy warm at best. Also, whereas before it
would take about an hour to heat a good hot tank for a bath it can now take
2 hours and, even then, I am only sitting in a fraction of the water I used
to as the water does not get anywhere near as hot.
Any positive suggestions please?
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