Well I got the new element - it was the 27inch one - it is now fitted and
working ok. But you are correct, and I was a bit lucky! I can see that there
are many possible pitfalls and that some luck is needed. First of all (spot
on, Adam) there was an isolation valve between the header tank and the
cylinder - but the damn thing didn't work (not until some banging, WD40 and
lots of heat were applied anyway!).
Then came the actual job of getting the old one out - and it was a very old
one! - the cylinder was replaced in 1996, but I think that the immersion
element was much earlier and had been re-used. First of all the proper box
spanner that I got wasn't a very good fit - it was too big, I think that the
element flange hexagon was an imperial size. I had sprayed WD40 on it some
hours earlier - as recommended here, but I didn't have time to give days as
advised. Even after wedging the box spanner to get a decent fit, and tapping
it with a hammer, it still wouldn't budge.
Thankfully, after using the heat gun on it for a fair time (choking myself
on fumes from the cylinder lagging and setting off the smoke alarms in the
process!) I got it to move - hurrah! As I took it out I was surprised to
find the cylinder full to the brim - even though I had the isolation valve
closed and the hot taps open (with no water coming out of them). By placing
a couple of towels around the immersion heater hole and gently pulling it
out, I was able to clean up around the fitting and put the new element in
place without there being much water splashing about.
Yep, I think it could be a real sod of a job if things went badly wrong on
you. As it was I had real visions of having to replace the entire cylinder -
at around £200, not to mention loads of work and hassle - not a pleasant
prospect. Very grateful that it's done - and many, many thanks once again to
everyone for their help.
If I could pass on one or two tips on the basis of this experience, I would
1. Make sure that the isolation valve (if there is one) supplying the
cylinder is functioning ok before you start.
2. Tie up the ball valve of the expansion tank in the loft as a precaution -
better than turning off the cold water supply to the whole house (could be
while before it can be turned back on again!).
3. If your plumbing is quite old (like mine!), and things like stop taps and
isolation valves haven't been disturbed for a while, it might be worth
having a pipe freezer kit on stand-by.
4. Make sure that you have plenty WD40 and a heat gun available.
5. If the old element is quite stubborn to shift, and you need to give it a
few bangs with a hammer, make sure that the cylinder is full of water to
lessen the chances of damaging it.
6. Best of luck - you might need it!
I know that. But, although they were open, water had stopped flowing from
the taps. Normally you can draw a fair bit of water from the hot taps even
though the supply is turned off - presumably half empty the cylinder! In
this case the isolation valve was working ok - although it wasn't to start
with - so why was the cylinder completely full when no water was coming out
of the taps?
Unless there is a drain cock fitted on the cold water input to the
cylinder, you will never be able to empty the tank just by running the
taps if the hot water comes from the top of the cylinder (as is the normal
way of doing things).
Cold water comes into the bottom of the cylinder from the header tank in
the loft, and displaces the water from the top of the tank through the hot
water output at the top. If there is no drain cock fitted, the only way to
empty the cylinder is to loosen the cold water inlet pipe and continually
mop up the water as it leaks out of the cylinder. If the cold supply to
the cylinder and the bath tap are from the same pipe (ideally not, as this
would restrict the flow with the hot and cold taps running together),
turning the cold tap on would probably drain some of the water out of the
cylinder until it drops to the level of the tap.
When I replaced my cylinder, I made a T junction on the cold water inlet
pipe just before it went into the bottom of the cylinder. I reduced the
outlet to ½" and connected a short piece of pipe with a blanking plug at
the end. I fitted an isolating valve between the junction and the blanking
plug. This method means that the blanking plug will ensure that there are
no leaks, even if the isolating valve is accidently turned on. The
isolating valve means that, after removing the blanking plug, I have
complete control of the water flow when I want to drain the tank. I then
just stick a hose where the blanking plug was and run it downstairs into
If the isolating cock is between the header tank and the cylinder, turning
it off will prevent any water flowing into the cistern and the water
should stop flowing from the hot tap as you turn the cock off. If you only
turn off the water at the mains, then you would have to drain the header
tank as any water would still be able to flow from the header tank to the
Thanks, I see all that perfectly clearly now. We do have such a drain cock,
as you describe, already fitted at the cold water supply to the cylinder. Of
course this would only needed if the cylinder needs to be replaced. As I
have already discovered, the heating element can be replaced without too
many problems even if the cylinder is full.
Of course. I was basing my (confused) thoughts on the fact that when we lose
our water supply here (a regular occurrence at one time) we can continue to
draw water from the hot taps for some considerable time. I realise now that
this is simply because the header tank is full and continuing to feed the
hot water cylinder.
Less to go wrong and no worries about get an unintended hot or cold
shower from a tank in the roof which gets full of crud, or a hot
water tank that doesn't vent properly!! Oh you also get an airing
cupboard when yu take the cylinder away!
Also it releases the tanks from the loft for use on the allotment. I now
have 6 of them collecting rainwater coming off the shed and greenhouse.
Whenever I see the signs of this work going on I stop and see what's been
thrown out on the drive or in the skip.
Because I have a bath full of water always available - and it costs
almost nothing to _keep_ it hot. (heating a new tankful is another matter)
No electric system will give you a bath full at 5 minutes notice.
Why keep a tank constantly full of hot water at todays elec prices?
Most cylinders are heated by a regular or system boiler and so heated at gas
prices and not at electric prices.
If the regular/system boiler fails (far less to go wrong than a combi) then
you have an immersion as a backup.
The hot water for a house is best delivered by what is wanted or needed.
A single person or a couple living in a flat or small house may be OK with a
A family of 4 in a 4 bed house with ensuites csnnot use a combi and say that
their HW experience is good.
There are pros and cons to all setups.
- Alternate tighten/loosen with any stuck nut
- Fit an isolator ball-valve in the CW tank supply
- Check the terminals after 6 months for loosening - Neutral as well
Whilst on the subject of tanks, what is the min height for a
combination tank (CW+HW) above a sink/bath tap?
(S)He may be referring to something like "Harcopak instant plumbing". My
house, built 1973 ish, had this when we moved here. In the airing cupboard
was an angle iron frame with the cylinder in the bottom half, then a tank
above with a small tank in that for the heating feed. Both parts of this
upper tank were fed from the rising main, and each had a ball valve in it. I
think the house was built round it, when the tank leaked, I extended the
pipes up into the loft, put in two plastic tanks, and removed the
arrangement below. But even removing the airing cupboard door I couldn't get
it out. I had to cut the frame apart with an angle grinder, which of course
made me extremely popular.
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