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Posted By Topic: Changing hw element with a full tank

Aug 18 2019 20:52

Just watched some YouTube videos of some guys changing hw elements without draining the tank.Even an ad for a plastic water shoot to drain into a bucket for initial water discharge.Anybody tried this and was it successful?

Aug 18 2019 21:05

I've heard stories that it is possible to do this, but I would never attempt it. Over the years I've replaced dozens upon dozens of elements and getting everything to sit just right is damn near impossible. Not to mention a lot of areas in Hawkes Bay have very high lime deposits and tanks need to be cleaned out. If I have had trouble draining a tank I've always called in a plumber.

Aug 18 2019 21:38

They do it without draining in Australia where most of their hot water cylinders are outside the house.

I wouldn't try when the cylinder is inside.

Also I was told a long time ago that there's a chance of the cylinder collapsing when draining due to the negative pressure, if there isn't a large enough vent to the tank or the relief valve is faulty. But I've never had any problems.

Just remember to crack the element slightly before draining the water out.

Aug 19 2019 08:47

Certainly can be done, but NOT a good idea unless no other option is available.


Aug 19 2019 08:50

Have done it many many times, preparation is the key. If the old element is distorted your buggered but otherwise it is easy. Sacks, old towels, whatever to soak up the surplus makes sense but of course if the water is hot don't bother. Remove the stat and disconnect the cylinder wiring especially if its fabric covered, loosen the old element to the last thread (it will dribble a bit) then using your strong most dexterous hand get a hold of the new element ready to insert when ready use the weak hand to pull the old one out and quickly insert the new element. If you are well co-ordinated you will be surprised how little the amount of water needs cleaned up. I wouldn't bother doing it in a million dollar house but then something like that would hopefully be plumbed properly. Nearly all that I have done were in older houses.

Aug 19 2019 10:23

I guess some kind of a bucket system with an adjustable shoot that can be put up around the element would help also.

Aug 19 2019 11:16


In the company I work for we use the services of a plumber to drain and replace the element. We do the electrical side (disconnection and reconnection). Part to do with responsibility: if the cylinder fails and leaks, then it’s the plumber responsibility.

Aug 19 2019 11:57

Yeah in the good old days sparkles just did it anyway.

Aug 19 2019 11:58


Aug 28 2019 22:12

Tried it once. Made a mess. I warned them beforehand, but it was still an embarrassing experience.
I mostly do dairy elements now. They're always really easy, just open the big valves and dump it all on the floor.

Aug 29 2019 07:06

I tried it once on an outdoor cylinder, it failed miserably, at least it drained quickly though

Aug 29 2019 08:32

what age is the house and what's the floor material or is it a concrete floor? if it's a wooden floor i just drill holes in the floor, make a dam with towels and let it go or drill through the center of the element and have a tapered adapter made to bung in the hole with a hose coming out, advise the customer that it will be long and slow this way or fast and wetter by unscrewing the whole element, give them the choice.

Aug 29 2019 08:53

Why wouldn't you just drain it?

Most times, there's a drain connection. Sometimes it has a valve and a connection for a hose.
If not, you can disconnect a pipe on the cold feed to drain it.

Aug 29 2019 10:26

That is a scary idea!
The old cylinder threads are usually a bit corroded so my chances of getting the new element straight in while a flood of water is coming the other way are not good.
I'll stick to draining first.

Sep 12 2019 06:45

An element is basically a component of a hot water cylinder .Does your license allow you to replace this component which is essentially a plumbers job ? While it is an easy fix and sometimes expedient to do so and there are countless "how to" on the interweb and youtube, do you observe plumbing regs and the building codes G12 specific to hot water cylinders while carrying out the replacement ?
Asking for a friend

Sep 12 2019 07:27

So would you have the home owner call in a plumber first to change the element and then call in an electrician to connect it and test?
There comes a time when madness needs to be challenged.
Seen to many jobs where plumbers have changed an old cylinder and connected the wiring themselves with old 10 amp switches for 3kw elements/ removed the old metal conduit and left no earth/ wiring so tight and covers unable to be opened because pipes run across the face.
Changing an electric element in a cyclinder is a sparky job. From a plumbing side all we have to do is make sure it doesnt leak and thats not hard and cheapest for the homeowner.

Sep 12 2019 07:59

I do understand that in most cases this is a simple fix and at less cost to the homeowner if you were to replace the element component as well as dis/reconnecting but my question is really about observing the requirements of their plumbing regs and the G12 while doing so. Specifically that components introduced should not contaminate the potable water.

Sep 12 2019 08:08

The only component introduced is a new element, really don't see what your getting at

I agree its a sparky job to do the element, see far too many dogdy plumbers reconnections after changing a element

Sep 12 2019 08:31

I gather then you are not aware of any plumbing regs about the use of elements on all components in contact with potable water must comply to a standard in G12 . I agree a plumber should contact an electrician to wire it up

Sep 12 2019 08:59

geegeeup - Not really sure what your concern is? Any replacement element that's readily available would be suitable for potable water.

The only question is whether a plumbers license is required to replace an element. Do you have an answer to that question?

And I wouldn't place too much faith in G12, considering the number of errors it contains regarding pipework bonding requirements.

Sep 12 2019 09:29

Yes I guess that is my question do you need a plumbers license to charge for doing the job ?
Recent changes to the G12 make it must to ensure your elements meet the guidelines as in AS/NZS 4020 and all elements are not created equal. some will leech unacceptable levels of lead and nickel into the water .

Sep 12 2019 11:03

It's actually a valid question; especially in these days when if anything goes wrong people get lawyered-up.

Working outside licensing requirements could result in PL insurance being invalidated and any accident would bring in Worksafe.

I agree Plumbers shouldn't do the disconnect / reconnect unless holding a relevant PL (eg associated Tradesperson); and if we expect them to observe that rule then we should equally not be breaking their rules.

I don't know the answer, but I believe there's a similar provision where an electrician can be approved by PDG Board to do such work. Not immediately clear from PDG Act, nor from PDG Board website, whether this is "sanitary plumbing"; but appears to be. And while there's a exemption for tap washers, haven't found one for elements yet.

Sep 12 2019 11:25

While the cylinder is draining I prep my new element with graphite paste and hemp. Who here uses the supplied seal that comes with element and who uses hemp? I've never had one leak yet?

I have come across cylinders that have no drain facility, not even under the house directly below the cylinder. It was also an old house and had the original 50s cylinder.
It had an element cover that bolted to the long stud on the element body but a local franchise sparky replaced the element and couldn't figure out how to refit the cover so just left it with the little plastic cap over the terminals and everything else exposed.
As the original cover was long gone I cut a hole in a metal rittal box and refit the element and thermostat through it. Worked a treat.

Who here also replaces the thermostat when the element has blown?

Sep 12 2019 15:46

Changing the thermostat is not usually necessary Apart from mechanical failure the main reason for these to not operate successfully is an calcified pocket.Apart from the 4020 contamination issue in G12,
nine times out of ten you will be fine with replacing an element like for like but you should have knowledge of the water in the area in which you are working to ensure a more correct replacement is used or there could be warranty issues and you could find yourself doing the job again. Have spoken to PDGB who admit this is a grey area and will get back to me with -sometime.


Sep 12 2019 15:51

geegeeup I have come across several instances where the fault current when the element shorts has caused the contacts in the thermostat to weld themselves closed or severely affect it's accuracy.
If it it is an old thermostat I advise the client of this and let them make the call if I change it or not.
No one wants a boiling cylinder.

Sep 12 2019 17:40

I prep my new element with graphite paste and hemp. +1

and who uses hemp? I've never had one leak yet?

In a previous career, I serviced commercial dishwashers, soon found out that hemp and graphite paste works way way better than seals and thread tape

Sep 13 2019 13:22

AlecK - I have clarified this with PDG board who tell me that while the said definition does not exclude replacing an element they are aware that unlicensed technicians do so and are quite happy for this to continue. However they recommend that they be familiar with any Standards used to select an element and seal.


Sep 13 2019 15:27


Amounts to: we're not allowed to, but they'll turn a blind eye as long as we don't stuff it up.

Sep 13 2019 23:10

May have to learn to do graphite and hemp seals. Have only used tape seal and never had a problem with weeping elements until they changed from the soft gaskets that were about 1.5mm thick to those very thin hard plastic ones. Have learnt to be very careful with cleaning down the threads and I use wet and dry sand paper to smooth down the element boss. Even then sometimes it takes several attempts.

Sep 14 2019 08:32

Hemp and graphite always worked for me.

Sep 14 2019 11:19

AlecK -Not all doom and gloom ,a quick read of their standards and building code G12 will tell you all you need to know about hot water cylinders and their components and the replacement ,and pressure rating the gasket has to comply with.Cylinders are often supplied with the very basic element that is not suitable for the water conditions and so a like for like change may result in a premature failure and also void any warranty. Warranties are usually seem very generous in time but there are often several wriggle room conditions attached.
No difference really to you are replacing an oven element ,referring to the models' manual and any bulletins that may have been issued.

Sep 14 2019 11:37

So your saying plumbers take the time to check the type of element and would change it if it wasn't the correct type for the water????

Sep 14 2019 12:43

"graphite and hemp" the beauty of this as a seal for water is the fact that contact with water causes the hemp to swell, so while there might be some slight seepage initially, it stops pretty quickly.

Sep 14 2019 13:36

Will J Yes-if they dont want to void the cylinder warranty and do a return repair at their own expense . For instance Rheem are quite clear on this.

Sep 16 2019 18:01

Going back to the original post there was a suggestion when I served my time some 50 years ago that one could put a cork in the exhaust on the roof so little water would come out when the element was removed. Only problem could be depending on the length of exhaust that the vacuum would cause the cylinder to implode. Also if one forgot to remove the cork there could be a danger of cylinder explosion. Of course one could not do that today as it would be necessary to scaffold the roof to gain access to the exhaust!
Second point I concur nothing like hemp and graphite much better than PTFE tape but also now there are some very good Loctite solutions for metal threaded fittings.
On the second string geegeeup has done a very commendable community service in alerting the general populace to the metal leaching problem. It would have been helpful though if he had provided statistics on the number of fatalities and serious illnesses caused through leaching of the metal contaminants from the elements.
I am sure that this problem is not widely known, I have spoken to a plumber friend and he had never heard of it and just uses the elements that he gets from the merchants or else come in the cylinder. The elements on the merchants shelf do not seem to have any identification warning the buyer of the problems that can arise although there does seem to be a couple of different sheath materials available.
The sponsors of this page should probably be putting pressure on the health authorities and work safe to alert the problem with widespread advertising and notifications to the trade and public. Probably should also be warning labels similar to cigarettes on the actual elements as I'm sure many do-it-yourself people would change their own, they are widely available and our local Mitre 10 even hires the socket spanner to remove them.
It is indeed another issue that we have to worry about.

Sep 17 2019 08:48

It's definitely important to use the appropriate element for the cylinder; nickle plated for copper cylinders, tin plated for steel.

That's nothing to do with leaching, and everything to do with galvanic corrosion. Mains pressure cylinders are glass-lined steel, and have sacrificial anodes; which is why Rheem (for one) specify a tin-plated element. It's also why they are a "handle with care" product, as bump-crashing them around can crack the lining. Using a nickel-plated element will shorten the life of the cylinder, first by eating away the anode and then attaching the other metals.

Also in some areas due to water quality you may need to use special types, eg "lo-lime" or incoloy; just in order to get a decent sort of life out of the element.

As for leaching, it is a very slow process. It takes time; and is undetectable unless water sits still for long periods. Which is why govt advice to those with copper pipes is to run the tap for a few seconds if the water has been left sitting for a period, eg while away on holiday.

The element of a HWC will contribute SFA, as compared with the cylinder itself (if it's copper) and the pipes.

Even if there's detectable level of metal in the water; you can't absorb it through the skin while having a shower or bath; you have to drink it. LOTS of it, over a LONG time, to suffer any effects.

Water from a HWC is seldom ingested. Most people drink, and fill their kettles / pots, from the cold tap.

So can we please not let this thread about the practicalities of changing elements get side-tracked onto fear-mongering about what might be in our water in barely-detectable trace amounts?

Extract from Ministry of Health document:
What can I do to avoid drinking water containing heavy metals?
Taps contain the heavy metals, and are main sources of heavy metals that are found in drinking water in most houses. Water with safe levels of metals can be obtained by flushing a small volume of water – 500ml- from the cold tap before water is drawn for drinking, cooking, or brushing your teeth.
If your house has a rainwater supply, check your roof and guttering for materials that may contain metals that could contaminate the water: lead flashing, lead-headed nails, and lead paint, for example. These should be replaced if you find them.
Flushing cannot easily rid drinking water of copper, if copper is being released from copper pipes. Copper is much less of a health concern than the other heavy metals, and levels that might be a health concern do not arise often.


Sep 18 2019 06:57

lecK & Frostybird .Thanks for the feedback. I understand that the Master Plumbers have made a submission to MBIE to introduce Watermark into NZ .This will likely be a while but however in the meantime G12 states that all components in contact with potable water should comply with AS/NZS 4020. The definition of potable water includes oral hygiene,food prep, and utensil washing as well as human consumption. The definition of should is will . While quite a recent requirement (2018) the guidelines for acceptable levels of metals are as laid down in the ADWS which is similar to NZDWS with recommendations from the WHO.Leaching increases with rise in temperature and materials used in the manufacturing of elements may be over limits, which are very small. ie the limit for nickel is 0.02 mg/l.I have no data on the number of deaths or any sickness this causes but is recognised as a real threat by WHO.There are elements in the market that do comply and we have discussed the topic with various wholesalers but have met with a reluctance by them to take it on board with some saying that most of the elements are bought and fitted by electricians who will have no interest with following plumbing standard.Which is why I raised the subject.
A Rheem booklet that accompanies every cylinder is quite clear that the element provided is for the most benign waters and if the water in your area contains solids and contaminants then a more robust element should be used instead to avoid any warranty issues .Mind you the rest of the conditions are hard to meet as in regular flushing and descaling . A


Sep 18 2019 09:34

Actually "should" can only ever be a recommendation", it takes 'shall" or 'must" to set a requirement.
It only took a few moments to find that Min Health document via Auntie Google, and there's another one by Cawthron Institute; being a review of the literature.

So yes there's an issue, but it's a small one - and it has SFA to do with the topic of this thread.

Getting the element election wrong will have other, far more immediate - & expensive - effects.

But again SFA to do with the topic.

For a proper discussion of an off-topic issue - and so people can find it when searching - should start a new thread.


Sep 18 2019 17:52

- should start a new thread.
- shall start a new thread ?