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[Taxi_Driver]

My boiler is going to be offline for probably about a week 

So i want to fit an immersion heater to the hot water tank....so at least ive got hot water during that time...theres a 20amp supply in the airing cupboard...so should be a fairly easy install.

Been looking at them quickly and they appear to come in two sizes .... 11in and 27in....am i right in thinking the 27in are for 'economy 7' installs and the 11in ones are for 'normal tariff' installs 

Will a 11in heater be big enough for a gravity fed shower? On for about 10mins 

Cheers chaps

[The Sheriff]

Nowt to do with economy 7, Dave. The length of the heater depends on the size of tank you're putting it in. Most common size of tank is 36", so 27" heater. If you put 11" in (ooer missus), you just heat the top 11" of water.

[The Sheriff]

Just had a thought. If your cylinder has a coil in there for the pump to throw hot water through, it may be the shorter one that's needed. If I were you, I'd wait for someone that knows what they're talking about to answer. 

[Bigron]

If your HWS tank is a standard 40-ish gallon tank, there should be room for the 27" heater, which will give you a greater depth of hot water for your length of showering - especially if another person wants to shower soon after you.
Plumbers may correct me, but the 11" heater is there to heat the top section of water in the tank to back up the boiler heating coil.
I assume that at present you have a blanking plate where the immersion heater is to go?
Some months ago I had to replace my immersion heater and I learned a whole new lexicon of profanities!
After trying MANY different techniques, I ended up using the biggest, best-fitting spanner and long lever, with sustained but not massive pressure on the lever, occasionally giving it sharp taps to jar it undone.
PLEASE have the tank full of water before you start to undo it, but only to loosen it! Once loosened, drain the tank somewhat to lower the water level and remove the cap, to be replaced by your immersion heater, obviously. The body of water strengthens and supports the tank whilst you apply the Desperate Dan measures on the cap.
Do not be tempted to use sealant on the threads of the heater - that is why mine was such a son-of-a-bachelor to get undone!
Good luck.

Ron.

[Bigron]

I read STMO's post after writing mine....my tank has a boiler heated coil in it; no problem, the immersion heater avoids it - must have been designed that way?

Ron.

[The Sheriff]

Thanks, Big Ron, that's exactly what I thought

All the ones I put in years ago were just cylinders with the one heating element...27". But then I remembered that most probably have a heating coil nowadays.

The 11" are crap on their own though. If I try to leave my boiler off and just use the immersion heater, I get about half a bath of hot water.

[Taxi_Driver]

Just had a thought. If your cylinder has a coil in there for the pump to throw hot water through, it may be the shorter one that's needed. If I were you, I'd wait for someone that knows what they're talking about to answer. 

I never listen to your answers Steve.....they are usually rubbish 

[The Sheriff]

Just had a thought. If your cylinder has a coil in there for the pump to throw hot water through, it may be the shorter one that's needed. If I were you, I'd wait for someone that knows what they're talking about to answer. 

I never listen to your answers Steve.....they are usually rubbish 

Well....turns out it wasn't this time

[Taxi_Driver]

If your HWS tank is a standard 40-ish gallon tank, there should be room for the 27" heater, which will give you a greater depth of hot water for your length of showering - especially if another person wants to shower soon after you.
Plumbers may correct me, but the 11" heater is there to heat the top section of water in the tank to back up the boiler heating coil.
I assume that at present you have a blanking plate where the immersion heater is to go?
Some months ago I had to replace my immersion heater and I learned a whole new lexicon of profanities!
After trying MANY different techniques, I ended up using the biggest, best-fitting spanner and long lever, with sustained but not massive pressure on the lever, occasionally giving it sharp taps to jar it undone.
PLEASE have the tank full of water before you start to undo it, but only to loosen it! Once loosened, drain the tank somewhat to lower the water level and remove the cap, to be replaced by your immersion heater, obviously. The body of water strengthens and supports the tank whilst you apply the Desperate Dan measures on the cap.
Do not be tempted to use sealant on the threads of the heater - that is why mine was such a son-of-a-bachelor to get undone!
Good luck.

Ron.

Ive no idea if the present tank can take an immersion heater.....but its going to be replaced first off...(its 32 years old i reckon at least) so first job is new tank with an immersion heater fitted 

Thanks for your input....didnt realise the water help strengthened the tank 
But as a new tank will be going in....the heater will be fitted before it goes in

27in heater....seems to be the way forward atm  and TBH 11in of hot water doesnt seem very much to me 

[Taxi_Driver]

Thanks, Big Ron, that's exactly what I thought

All the ones I put in years ago were just cylinders with the one heating element...27". But then I remembered that most probably have a heating coil nowadays.

The 11" are crap on their own though. If I try to leave my boiler off and just use the immersion heater, I get about half a bath of hot water.

So are you saying you have a little one thats no good to man or beast 

[4x4]

27" heaters are for single element tanks where it is screwed in from the top near the hoidioter outlet
11" heaters are fitted where the element can go in the side,normally 2 if economy 7,bottom is main heater on economy 7,left on all the time,top element is a booster,if you run out and tops up the heat 

[Taxi_Driver]

27" heaters are for single element tanks where it is screwed in from the top near the hoidioter outlet
11" heaters are fitted where the element can go in the side,normally 2 if economy 7,bottom is main heater on economy 7,left on all the time,top element is a booster,if you run out and tops up the heat 

Ah right ...cheers....actually you have just reminded me....i used to live in a house with economy7 heating....the hot water tank in that house used to have two heaters....bottom heater on all the time (well all night) top heater used for topping up  27in element it is then 

[Bigron]

Just a quick not for clarification - your new tank will have the heater fitted by you? If so, use just grease on the threads and the gasket, and hand tighten it. Fully tighten it when it is nearly full of water: same reason as before.
Nowadays, the Safety Elf decrees that the thermostat in the heater cannot be set as high as in earlier years, so as I like a lot of water in my bath, it is cooler with the extra cold water I have to add to get the level I like!
Bloody H&S rules!

Ron.

[4x4]

Boss white to be used on the thread and gasket,cant use grease as its not a sealant 

[Bigron]

4x4, I agree, and yet I don't. Boss white is great stuff if you never, ever want to dismantle the joint and the parts to be sealed are small and prone to leak (i.e. under high pressure), but in this application the thread is so huge that when it sets, unscrewing results in major aggro, especially when cooked over the years by the heat from the immersion heater.
Sorry, but my bitter and expletive-heavy experience when removing my old one backs this up.
The size of the thread is also a benefit here, though, as it really doesn't need a sealant, apart from the high temperature lithium-based grease I used on thread and gasket last year - not a drip from it and I only finger-tightened it plus a fraction of a turn with the spanner.

Ron.

[Marks DTM Calib]

Don't use Boss white, it doesn't need it, the gasket will stop all leaks assuming the mating face on the element and tank is clean.

In fact I have hardly seen any installs that truly need Boss white, plumbers bodge we used to call it. 

Also, get at least an incoloy element (only a few pounds extra) or if your feeling very rich, a titanium one (about double the price). The most common cause of element failure is down to corrosion and water then gets into the element, the above are considerably more robust and corrosion resistant. 

[4x4]

Ive always used boss white on emersion heaters,prevents leaks and also saves doing a job twice,boss white isnt a bodge its for to make threads water tight,boss white and hemp is used on all iron pipe work aswell,boss blue is for use on gas only.

[Marks DTM Calib]

It is a bodge on immersion heaters as the threads are not designed to be the sealing surface, its the plain face of the immersion heater collar with the gasket that is. I would argue its not ideal on anything (other than maybe malleable iron threaded fittings) as none of the standard parts you get at designed to use it (and hence they were designed such that it was not required).

The issue with Boss white is that it secures the immersion heater units to well and can result in a torn cylinder if trying to replace later. 

[4x4]

I use it on both the gasket and thread,ive seen them leak when nothing has been used on them,ive changed a few in the past 28yrs working for myself ,bedford council and other plumbing firms in bedford,as for getting them undone,you take the risk,and do it gently,its same as undoing bolts on cars etc they can shear off,nothing different,just knowing your own strength,and using the right tool for the job ,but ive have been taught this way by tutors at college and when i was with different plumbers when an apprentice,its like using black gasket sealent on the cam covers near the cam pulleys,we do it because it works and in theory we only have to do it once.....

[dbug]

Do people still use Boss White?  Can you still buy it?  And hemp   Remember it well back in the 60s, along with "soldering" lead pipes.

PTFE tape, silicon sealants etc surely.

[4x4]

Ive had to solder old lead pipes in the past ,still buy hemp and boss white is still sold everywhere

[Tony H]

Don't use Boss white, it doesn't need it, the gasket will stop all leaks assuming the mating face on the element and tank is clean.

In fact I have hardly seen any installs that truly need Boss white, plumbers bodge we used to call it. 

Also, get at least an incoloy element (only a few pounds extra) or if your feeling very rich, a titanium one (about double the price). The most common cause of element failure is down to corrosion and water then gets into the element, the above are considerably more robust and corrosion resistant. 

Well worth the extra cost I replaced my last element twenty five years ago with a titanium one and it's still going strong 

[Taxi_Driver]

Don't use Boss white, it doesn't need it, the gasket will stop all leaks assuming the mating face on the element and tank is clean.

In fact I have hardly seen any installs that truly need Boss white, plumbers bodge we used to call it. 

Also, get at least an incoloy element (only a few pounds extra) or if your feeling very rich, a titanium one (about double the price). The most common cause of element failure is down to corrosion and water then gets into the element, the above are considerably more robust and corrosion resistant. 

Thanks for that tip 

I ask a college lecturer yesterday (that teaches plumbing, so i would hope he knows what he was taking about) , about adding a immersion heater to my existing cylinder, when he found out it was at least 32 years old.....he reckoned he wouldnt even attempt it....with the probable limescale build up inside it...

On the bright side, he offered me, a slightly larger tank than i have, which apparently has been used for a demo...then uninstalled and been sitting about for 6 months....and could give me the receipt for it (so i had the remaining 10years warranty on it)... He reckoned they paid £150 for it and would be looking for scrap value for it .... £50 ... bargain perhaps 

[Marks DTM Calib]

Very much struggling to understand the correlation between lime scale build up and 'knackered'.

For me, knackered is thin walled and holed (as the copper would corrode if it was not for the anodes inside it), lime scale will actually help that.

But if this is the thinking of the teachers then its no wonder the trade is in the state it is. 

[Bigron]

Having been a college lecturer (Electronics, not plumbing), I doubt the "selling off" story. It is exceedingly difficult to sell any college items to students, the system doesn't allow it.
I'm wondering if this might be a dodgy deal? Make sure you get a receipt, TD, if you do buy it.

Ron.

[Taxi_Driver]

Actually, scrap this thread about immersion heaters and hot water tanks.....

Think ive just spent £2.5k on having a Vaillant combi instead  Well actually i have 

The ecotec plus 831  But thanks for the info guys   

[The Sheriff]

Actually, scrap this thread about immersion heaters and hot water tanks.....

Think ive just spent £2.5k on having a Vaillant combi instead  Well actually i have 

The ecotec plus 831  But thanks for the info guys   

S'alright, Dave, we've got eff all else to do. No......really...

[Taxi_Driver]

Actually, scrap this thread about immersion heaters and hot water tanks.....

Think ive just spent £2.5k on having a Vaillant combi instead  Well actually i have 

The ecotec plus 831  But thanks for the info guys   

S'alright, Dave, we've got eff all else to do. No......really...

Well you have...except cleaning / changing your incontinence pads 

[05omegav6]

Actually, scrap this thread about immersion heaters and hot water tanks.....

Think ive just spent £2.5k on having a Vaillant combi instead  Well actually i have 

The ecotec plus 831  But thanks for the info guys   

S'alright, Dave, we've got eff all else to do. No......really...

Well you have...except cleaning / changing your incontinence pads 

Shopping and washing too don't forget... our Steve is a busy house wife

[Marks DTM Calib]

£2.5K for a crappy combi!

So £900 of boiler and £1600 to fit it

[TheBoy]

£2.5K for a crappy combi!

So £900 of boiler and £1600 to fit it

That's the way of the world now, esp with Corgi Gassafe trying to spread as much 'dangle berries' as possible 

Still, a combi may well work for TD, if he remembers not to put on the washing machine when taking a shower

[aaronjb]

I've had the washing machine on, dishwasher on, flushed a toilet downstairs and had the shower running at the same time (I wasn't in all three places, obviously ) - shower still worked just fine, didn't burn me, didn't freeze me and the house didn't explode and my combi boiler didn't catch fire..

[Marks DTM Calib]

The bigger issue is when someone runs a hot tap in reality (I don't think most washing machines have hot water feed these days).

That and they are annoying unreliable things and far from suited to a place with reasonable length pipe runs.

[Taxi_Driver]

£2.5K for a crappy combi!

So £900 of boiler and £1600 to fit it

A bit more on parts than £900.....the flue has to extended to go from the kitchen, thro a loft and out of a pitched roof. Everything is being ripped out (except rads and pipes) and replaced with new..plus magnaclean2 thingy and powerflush......that way im getting 7 years warranty on boiler  and 7 years labour warranty.

[Taxi_Driver]

The bigger issue is when someone runs a hot tap in reality (I don't think most washing machines have hot water feed these days).

That and they are annoying unreliable things and far from suited to a place with reasonable length pipe runs.

Boiler in the kitchen....bathroom next door.....no plumbing upstairs