Immersion heater element length

Page 2 of 3  


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 say that:
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!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
As I took it out I was surprised to

Why did that surprise you? I warned you.
The feed to the hot taps comes out of the hole at the top of the cylinder.
Adam
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@nospam.com (Farmer Giles) wrote:

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 " 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 the garden.
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 cylinder.
Roger
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Because you are asking water to flow uphill. Once the headertank is empty or isolated there is no pressure to the tank to force the water out of the top of the cylinder.
Adam
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
thank goodness for combi boilers!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Is that because combi boilers never break down?
Adam
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

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!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Steve
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
AJH wrote:

Cupboard I see, as it is no longer half full of tank. But how does it air?
Andy
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

We put a small rad + TRV in ours - works a treat.
That said, we also put our cable modem & router plus their associated power supplies in, too, so barely need the rad ...!
--
Martin


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

More chance of a combi failing than an immersion heater.
If you want the airing cupboard space then put the cylinder in the loft.
Adam
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

..
Why keep a tank constantly full of hot water at todays elec prices?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
AJH wrote:

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.
Andy
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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 combi. 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.
Adam
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Another note... - 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 as Live
Whilst on the subject of tanks, what is the min height for a combination tank (CW+HW) above a sink/bath tap?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Not sure I have seen those tanks.
Adam
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

(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.
Steve
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.