What to do if the element won't loosen
Try not to get frustrated - DIYers who allow a stiff immersion heater element to get to them often end up doing damage to their hot water cylinder and having to pay for the whole thing to be replaced!
So why isn't it loosening?
Some tradesmen or DIYers pad out the thread on the outside of immersion heater elements with things like PTFE tape, jointing compound, sealant or even super glue because they are worried about leaks.
Immersion heater elements that have been in situ for a long time can also seize inside the copper boss. This can make it more difficult to loosen and remove an immersion heater element from a hot water cylinder.
What can you do to solve the problem?
To help to solve the problem, you will need a blowtorch. You may also need a screwdriver and a Stanley knife if your tank is insulated with polyurethane foam.
It's possible to loosen the joint by applying heat around the edge of the immersion heater element. Make sure your immersion heater element is clear of all insulation, removing more foam if necessary. Unscrew and remove the thermostat, if you haven't done so already.
Step 1 - Apply heat
Apply heat around the edges of the immersion heater element with the blow torch.
This heat will cause the copper in the boss to expand faster than the metal at the base of the immersion heater element, which will loosen the grip of the screw thread inside the boss. This should make it easier to loosen the immersion heater element.
Step 2 - Attempt to loosen element
With a little luck, the application of heat should have loosened the immersion heater element to the point where it will turn when you tap your spanner handle with a hammer.
Repeat steps 1 and 2 until the immersion heater element is loose enough to move.
As soon as you can see it moving when you tap the spanner handle with a hammer, move on to step 3.
Step 3 - Remove immersion heater element
Once the loosened immersion heater element has cooled, remove it by hand.