[Closed] Removing an immersion heater element - hints and tips pls

Have you checked that they haven't just tripped out? There's usually a little button that pops out when they do.
Obvs check the power supply to them also. I've never had to take one out so can't help on that bit I'm afraid.

The copper in HW cylinders is very thin. Creasing the tank is the biggest problem, so yes, first couple of mm of loosening while tank full (though obviously with the feed turned off and hot taps opened). You might find a longer stilson wrench better than the normal tool, as it can provide a lot more leverage and control.

Are they definitely both in use? The other one could be some economy seven relic if you normally heat it using a boiler.

I’ve got a Box immersion heater spanner, and Plusgas … leave water in the tank for the initial loosening? Hit box spanner with a hammer to produce a shock to unlock?

I changed them a couple of times as a plumbibng reprobate:

- They unscrewed ok both times, using a box spanner and a few taps with a hammer. There is gasket to seal it so doesn't need mega torque. Be careful with plus gas in a cupboard.
- The tank needs drained, easy enough with some hose and carefully checking the connections
- When isolating and draining the tank one of the cheapo valves broke so ended up having to do a full water off a swap valve.

And my hard learned lessons for all DIY plumbing work:

- Always assume it will go to shit. Have buckets, towels etc to hand. Either isolate the whole water supply or know how to do it quickly. Ideally no where the street isolation is too.
- Never attempt it in the evening or Sundays. Highly likely you will need to pop out for a part you either broke or didn't know you needed.

Tomd - good advice!

The pop out fuse is OK. There's power to one of the elements. The other doesn't have power and suspect it's linked to Economy7

Is there a general rule as to which element is the top-up immersion, and which is the main tank (one's at the bottom, one at middle of tank)?

I couldn't shift mine and I used a blowtorch to heat the tank on the recommendation of a plumber. It needed a lot of heat as the tank acts as a heatsink - the blowtorch I used was one of those with a separate gas bottle and I seem to remember it went clang as it heated up, gently tapped the element spanner with a mallet and it turned easily. Not difficult but one of those worrying jobs with a good disaster potential.

There’s power to one of the elements. The other doesn’t have power and suspect it’s linked to Economy7

Is there a general rule as to which element is the top-up immersion, and which is the main tank (one’s at the bottom, one at middle of tank)?

So you're not sure if the E7 one is broken? Worth trying to swap over the power from one element to the other? You should know if the property has had E7 in the past because there are normally two separate distribution boards.

EDIT: Just re-read your OP - so you think you still have E7? You need to confirm and check so you know what you're dealing with.

If it's just the top one you have to change, you shouldn't need to fully drain the tank, just drop it until it's past the hole you are dealing with once you've loosened it off. The extra water in the tank helps stabilise it while you're heaving on the tool.

When I had one put in the plumber couldn't get the blanking cap off, took a lot of heat, swearing and a lot of elbow grease. Did eventually unscrew.....

Always assume it will go to shit. Have buckets, towels etc to hand. Either isolate the whole water supply or know how to do it quickly. Ideally no where the street isolation is too.

Pretty much sums it up.

Highlights include freezing a pipe, cutting the pipe only for the resultant icecube and a sizable portion of the heating system pour down my sleeve into my armpit.

New rule is now keep a pushfit (removable) of the correct diametre in my pocket whilst working.

@Aus - Apologies if you have done it already, but have you checked the resistance across the element terminals with the supply off?

I am not a plumber, but have replaced a few boiler elements in coffee machines etc. when repairing faults. I have been surprised a few times when the element was actually fine and something else needed replacing.

Edit: Just saw you put one had power. Still worth comparing the two to resistance values save you the hassle of removing it unless completely necessary.

To echo advice above, check the thermostat isn't at fault. They are in my experience more unreliable and can be changed without any messing around. Check for continuity across the terminals (with it disconnected) - if nothing then it's duff.

J

To third the advice, check the thermostat(s). It looks like the blue one is a replacement one, the brown/red one looks older. A cheap fix if that's so as Screwfix keep them.

Somewhere around 20 ohms for 3kW heating element.

couldn’t shift mine and I used a blowtorch to heat the tank on the recommendation of a plumber.

This is a good bit last resort method. I'd recommend cutting back a load of the insulation if you do this.

From experience, I recommend a Monument spanner:

https://www.zoro.co.uk/shop/hand-tools/basin-wrenches/361t-box-ring-immersion-heater-spanner/p/ZT1010803X?utm_source=google&utm_campaign=pla%2B%7C%2BHand%20Tools&utm_term=ZT1010803X&utm_medium=pla_css_3&targetid=pla-394858519378&loc_physical_ms=9044872&dev=c&gclid=CjwKCAiAxJSPBhAoEiwAeO_fP0hAGZ6AG3ZiyJzTIJnybjxYNkTpVn75CS4KM8X0LxOlqok_u-TtvhoCVx4QAvD_BwE

Box key, or pressed from flat spanner will just not allow sufficient leverage.

Cast spanner will allow to be 'tapped' with a mallet.

drnosh - just ordered that exact spanner.

I was getting zero resistance across the element. Didn't think to check the thermostat but will do that later. And will try switching the power over on the 2 elements.

The lower one will be for Eco7 as this was installed on all the local houses, hence no power when I checked in the morning.

I was getting zero resistance across the element.

Doesn't sound right, I wouldn't expect it to fail as a short, much more likely open circuit.

I can echo what martinhutch said above about the thinness of the copper. We got a plumber to replace a cylinder a couple of years ago and he put a crease (at the bend onto the emersion threads) in the new one putting it in. Thought he got away with it but it sprung a leak a few weeks later and had replace the whole cylinder again.

Once you're sure the elements are fubared, you can use a hacksaw blade to cut out the sealing gasket. Elements will then unscrew easily.

Doesn’t sound right, I wouldn’t expect it to fail as a short, much more likely open circuit.

Agreed. If it's a short, there's a blown fuse somewhere.

Easiest way to test an immersion is to switch it on and go look at the electricity meter, if it’s spinning/counting quickly it’s working.

But if you’ve got no resistance across the terminal it’s done for, they usually blow open.

Tips for changing- cut the fabric seal off, any hint the tank might twist, stop!
For fitting the new one a liberal coating of boss white before it goes in

Thanks all - have re-checked this morning and think I'm beginning to understand it.

The lower element and thermostat are fine, showing 20ohms at the element and the thermostat. It's linked to Eco7.

The upper element is showing no reading with multimeter on 200ohms, but the thermostat is fine (20ohms) so will replace it.

And thanks for the tip on cutting the gasket!

Is the immersion your only source of hot water and do you actually use the Economy7?

Given the potential for plumbing stuff to go wrong I'd just rewire the top one to the bottom - at least you'd get a full tank of hot water.
(Unless you actually only want/need half a tank)

Given the potential for plumbing stuff to go wrong I’d just rewire the top one to the bottom – at least you’d get a full tank of hot water.

This is what I advised a bit further up - is there a reason you don't want to do this, given that there is some risk of knackering the whole tank during the repair, which turns it into a significantly pricier and PITA job.

Thanks for all the advice, much appreciated.
Got a chance to go around and look properly with my multimeter, a bit odd. The couple only use the top up heating occasionally and don't want to heat the whole tank, so resistant to switching power supplies.

But on cleaning up the elements a little, I think both are fine and in fact, both thermostats non functioning. Removed both thermos and pull off the casing, and on both, the bimetallic (?) strip clicked back. Then tested them with multimeter and now both working fine. So just refitted them and kept my fingers crossed as water heating now!

In an old flat I had the immersion heater thermostat failed on. When I was out.

Came home to the wallpaper steamed off.

This happened the year after mine failed. If you're at all worried about the thermostats swap them out.

http://news.bbc.co.uk/1/hi/england/somerset/7179092.stm

Odd it exploded, it should vent to the header tank or at least ours does...

Although the input feed is at the bottom of the tank so pressure would push water down and back up the feed pipe - should still act as a pressure release.

Odd it exploded, it should vent to the header tank or at least ours does…

It explains in the story.horrendous accident

Ah, it was the header tank not the cylinder which failed.