Advice on removing immersion heaters.

[onzey]

Hi

Can someone advise me if it is better to try and loosen an old immersion heater while the cylinder is still full or should you always drain it first? I wondered if a full cylinder provides some protection against distortion while attempting to unscrew the old one. I have searched these forums and saw only one comment suggesting leaving the cylinder full.
(I need to replace both the main heater and the top-up heater)

Thanks.

 

[RacquelDarrian]

Call me daft but if you removed the heater element with the cylinder full wouldn't the water spill out all over the floor?
It would in mine.

 

[onzey]

Thanks for reply.

I didn't mean complete removal while the cylinder was still full.
I used the word loosen in the post to imply overcoming the initial resistance. I guess this might lead to slight leakage but could then start draining the cylinder straight away.

 

[nstreet]

If you had a water butt full of water and try to distort it by pressing does it distort, I think you find it will. My guess is it will be much the same with the cylinder. OK so you loosen, it but the cylinder ruptures in the process, not a great likelyhood but if it did big mess!.

I would personally drain first and take the chance.

Would lightly tapping around the old elements with a small hammer possibly loosen any scale or corrosion therefore making it easyier?

 

[croydoncorgi]

Hang on!

Cylinders are THIN! If you are rough with it when unscrewing the imm heater, it WILL split.

If the heater is top-mounted, it does help if the cylinder is left about 3 quarters full to give it extra stiffness / inertia against the impact of the imm. heater box spanner.

Other hints: put the box spanner on the heater boss and give the bar a couple of LIGHT taps CLOCKWISE before attempting to undo it. It helps break the sticktion between heater, gasket and whatever was put on to seal it before.
Be prepared to fail to unscrew it! If it won't undo with 'reasonable' force, then if you go further you'll rupture the cylinder. So stop before you damage it and PLAN the complete replacement rather than being forced into an emergency situation (like - have the replacement cylinder on-site before you risk breaking the old one!).
And when you eventually fit the immersion heater, do NOT use any sealant that goes solid!! I find LSX best.

 

[onzey]

Thanks for replies.

Drained cylinder (although stop tap on cold feed pipe won't turn completely off) and have given both heaters a few taps but neither will budge. Will either try and get a more beefy box spanner tomorrow and try again and/or call in plumber. (It's a pain filling the bath with saucepans.)

 

[kevplumb]

heat sometimes helps

 

[ChrisR]

If you have 2 separate heaters they presumably ARE in the side of the container, so yes you do need to drain almost all first!

I would heat a lot (avoid igniting insulation) and use a cast iron box spanner, which you can hit. If no prompt undoing I use a 2 ft Stillson on a box spanner, controlled but persuasive.

At the death you can cut through the brass of the heater bit. Drill, then jgsaw + padsaw or Dremel.

 

[onzey]

Thanks for further ideas.

However, plumber I've used before was able to fit me in this morning so got him to do it. Upper heater was a real pig but eventually gave in to box spanner with extra bar for more leverage. (Cylinder is now a bit distorted where this heater goes in but some of this is probably from attempts by myself and neighbour to remove this swine when it first failed a few months back)