Replacement E7 Immersion Heater

[SteamyTea]

I am finally going to have to do the element replacement next week.

I have a Super Seven cylinder (about 30 years old) and need to change at least the bottom immersion element.  The cylinder is approximately 18" (0.46m) wide and 60" (1.52m) tall.  When I try and measure it it is a little wider because of the pitifully small amount of insulation, about an inch all around it.

Now having a quick look on the interweb, I can get 11" or 14" elements and they can be made from copper, copper and incoloy, incoloy only and seemingly titanium.

How as the last element lasted almost 30 years, and I am in a very soft water area (not always good as things dissolve in water, eventually), what should I go for and where is a good online store to get them from.

 

So length and material, and where from.

 

Cheers.

[Jeremy Harris]

Copper should be OK, as with water that is slightly acidic, and hence a good electrolyte, you don't want a different metal if you can avoid it.  A 14" element should fit fine in an 18" cylinder, I'd have thought, but if you're at all concerned there would be no significant performance difference from fitting an 11" one.

 

Any reputable supplier should be OK, as these things seem to be pretty generic.

 

Your challenge is going to be getting the old one out - they can be really tough to remove when they've been in for a few years, and being a 30 year old one I bet it's been fitted with hemp and boss white, which won't help.

Edited January 6, 2018 by JSHarris

[SteamyTea]

I thought copper would be OK.

May have to get a totaly new cylinder when I come to get the thing out.  They seem to be costly now circa £400.

[Jeremy Harris]

About £350 inc VAT, plus carriage, from Newark: https://shop.newarkcoppercylinder.co.uk/vented-copper-cylinders/direct-economy-7-cylinders/1500x450-direct-e7-copper-cylinder

 

Might be a struggle to fit a newer cylinder, as the extra insulation may make it a tight fit.

[Onoff]

Lots of info here:

 

http://www.thermcouk.com/immersion-heater-info/

[SteamyTea]

I have a little spare room, what I stuffed full of insulation.

I could also go for a small one as I don't need as much water as it can supply.

Do they all have the holes in the same place?

[Jeremy Harris]

With Newark, they will fit the holes wherever you want them, as they are made to order.

[SteamyTea]

Thanks @Onoff, that seems to answer most of it

[ProDave]

Try to slacken the heater a little bit while the cylinder is full. At least get it to turn a bit so you know it will undo.  Once the cylinder is empty the force needed may move the cylinder if you have not cracked it first.

 

Have some towels ready as once cracked it will likely weep a but until emptied.

[Onoff]

Give the thread a good squirt of penetrating oil a few days beforehand.

 

https://www.toolstation.com/shop/Automotive/d60/Lubricants+%26+Sprays/sd2795/Penetrating+Oil/p62311

[SteamyTea]

Is WD good enough, I have some of that to hand.  Or I have a trip to Truro.

Just noticed they have a branch in Penzance

Edited January 6, 2018 by SteamyTea

[Jeremy Harris]

I've always found that a bit of diesel works pretty well, better than WD 40, but pretty much anything that will penetrate and help to unstick the thing will help.  Older immersions had a fibre gasket as a seal and that seems to be most of the problem, rather than the threads.  The last immersion I fitted had an O ring, and was fitted with a smear of silicone grease, so I'd guess these newer ones are a lot easier to remove.

 

I buckled the top of the cylinder the last time I removed one, luckily without doing any serious damage, but that was after copious applications of penetrating oil etc.  The problem there was that the fibre gasket had stuck tight to both sides, so when it did come apart it was because the gasket just tore itself apart.  IIRC, the threads weren't stuck at all, it was really just the fibre gasket that was the main problem.

[SteamyTea]

After 30 years being in place, it may well be a bit solid.

 

If I manage to get it out, how many times should I wrap the PTFE tape around the thread.

And are all the threads the same size 2 1/4 BSP?

[Jeremy Harris]

Shouldn't need PTFE tape.  It will either seal with a fibre washer or an O ring and both seal on the flange, not the thread.  Usually there's no need to put anything on the thread, but I know from experience that some old school plumbers put boss white on everything as a matter of course. hence my earlier comment about that helping to get the damned things stuck in place.............

Edited January 6, 2018 by JSHarris

[Nickfromwales]

The fibre washer will suffice on its own, and do not use PTFE . 

The number one thing is getting a bit of emery cloth and cleaning the boss immaculately before fitting the new one. Remnants of the old washer is the number one cause of leaks. 

Whilst full and in use, connect a hose and open the drain off, as that'll be your biggest nemesis. Once you open it and prove it, that's one thing less to piss on your chips. 

With the immersion, get hold of the obligatory box spanner, but do all you can to get hold of a 3' stillys as that'll make cracking the immersion just so much more controlled. A bit of patience and effort there will pay dividends. There's no real advice other than to make sure your turning it, rather than pulling it off centre. It's quite hard to keep an eye on that as your perspective changes as you stand up. It'll either turn or it won't. If your tank is in any half decent shape then I'd go for @ProDave's method of keeping the cylinder full so it's counter weighted ( with the cold header tank empty first of course which will happen just by turning off the mains and opening a hot tap ). If you fear it'll fail then empty it slightly so the water level is below the boss. 

Iirc you have a shower pump. Remember to isolate the pump as this process will disturb all the sediment. Open them 24 hrs later when it's all settled  

Enjoy. 

[ProDave]

Take care when cleaning off the remains of the old fibre washer not to scratch the surface of the flange. You want that to be nice and clean and flat.

[Jeremy Harris]

Is this where we start the sweepstake on whether or not the old immersion comes out at all?.............................

 

I will freely admit that I struggled for hours to replace an old one once, it was well and truly stuck tight.  That was in a house in Cornwall, too.

[joe90]

35 minutes ago, JSHarris said:

Is this where we start the sweepstake on whether or not the old immersion comes out at all?.............................

 

Yup, we are all ears Nick. I have some 24 inch stilsons if you want ?

 

could you not burrow into the fibre washer around around the edges to get some sort of release fluid into the washer itself ( but careful not to damage the flange)?

[Jeremy Harris]

7 minutes ago, joe90 said:

could you not burrow into the fibre washer around around the edges to get some sort of release fluid into the washer itself ( but careful not to damage the flange)?

 

With the benefit of the experience of removing one that had been in place for around 30 years or so, I'd say that might work.  The fibre washer is the problem, as it will be bonded on well to both the immersion heater and tank flanges.  They always seems to tear when you remove an immersion, so anything that makes it easier for the washer to tear and so allow the immersion to unscrew more easily seems to make sense. 

[ProDave]

My normal philosophy is to try and crack it open with the tank full.  If it moves I proceed. If the tank starts buckling, then I abort and advise the customer a new tank is needed and hand the job to a plumber.

[Nickfromwales]

I went to one leaking copper cylinder when young and keen ? and grabbed the cold feed pipe to show how bad the corrosion was, and that it was there that it was leaking from. As I put my hand on the pipe it pushes into the cylinder and the entire contents ( 115l or so ) emptied into the room in the wink of an eye. It presently disappeared into the floor void and all I could hear is the kid downstairs saying "mummy, the tellys gone off". Every drop went down the back of the telly, dvd, sky box etc. 

Another top day at work. They went through their own insurance after I took a photo of the knackered Union as I pointed to the hole in the living room ceiling where it was evident it had been leaking for years before I got there. 

Still got the old pulse racing though. ?

[bissoejosh]

Our ancient one packed up on Christmas eve just gone.  I was too scared to have a go and be without any HW over Christmas - luckily we have an aga which tops up the water enough for short showers. 2nd of January I set about it - 3 sharp blows with a lump hammer on the immersion spanner with a tank just below full and it was loose. Drained it down and replaced in about 20 mins. Pot luck really from what I've read, it'll either be kind or a sod.... Good luck!

[PeterW]

The trick is the sharp tap first - and I’ve always gone clockwise too ..!! It’s enough to jar it before giving it the shock treatment the other way. 

 

A few light taps on the immersion itself with a hammer can sometimes release any scale holding it in. 

 

If  it’s a fibre washer then a thin smear of Vaseline on the washer and the threads can help when you nip it up tight but don’t do this if it’s an O ring. 

[SteamyTea]

I am away for a few days, but have taken all the advice on board.

Looks like it will be a job for next Sunday now.

I have had a word with my not unattractive, single, blonde, European neighbour about using her shower if it all goes tits-up.

That could cost me