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  1. #21
    VoidMaster
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    Default Re: Two of the four elements donít work properly on my stove

    I know what I'm talking about 65 to 70 degC at the tap is fine to stop Legionnaires any hotter and you risk burns to older people who have slower reaction times and get burns easily. You have to put in tempering valve if you want to have hotter water in the tank and still not burn old people at the tap.

    "Legionella bacteria is commonly found in water. The bacteria multiply where temperatures are between 20-45įC and nutrients are available. The bacteria are dormant below 20įC and do not survive above 60įC"

    "Hot water should be hot. Storage of hot water should be above 60įC so that any Legionella can't survive. Distribution of hot water should be at 50įC or higher."
    It's not the least charm of a theory that it is refutable. The hundred-times-refuted theory of "free will" owes its persistence to this charm alone; some one is always appearing who feels himself strong enough to refute it - Friedrich Nietzsche

  2. #22
    Old guy
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    Default Re: Two of the four elements donít work properly on my stove

    zqwerty's advice is spot on. Get a thermometer and take an accurate measurement at the tap and then decide what to do from there depending on the result.

  3. #23
    Senior Member piroska's Avatar
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    Default Re: Two of the four elements donít work properly on my stove

    Quote Originally Posted by barryk View Post
    . I found out from watching videos that the elements used in hot water cylinders are 3000-4500 watts.

    Er....commonly in NZ they're 2K. You can get 3K.
    Ex-pctek

  4. #24
    Senior Member piroska's Avatar
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    Default Re: Two of the four elements donít work properly on my stove

    Quote Originally Posted by zqwerty View Post
    I know what I'm talking about 65 to 70 degC at the tap is fine to stop Legionnaires any hotter and you risk burns to older people who have slower reaction times and get burns easily. You have to put in tempering valve if you want to have hotter water in the tank and still not burn old people at the tap.

    "Legionella bacteria is commonly found in water. The bacteria multiply where temperatures are between 20-45įC and nutrients are available. The bacteria are dormant below 20įC and do not survive above 60įC"

    "Hot water should be hot. Storage of hot water should be above 60įC so that any Legionella can't survive. Distribution of hot water should be at 50įC or higher."
    https://www.stuff.co.nz/dominion-pos...-water-systems

    70.
    Ex-pctek

  5. #25
    Senior Member Paul.Cov's Avatar
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    Default Re: Two of the four elements donít work properly on my stove

    Barry, it's screamingly obvious your hot water system is leaking somewhere. Stop fretting about the thermostat or the element, or the electrics.

    There are two very primary places to start your investigation for leaks.

    If the system is old, it's probably a low pressure (gravity feed) hot water system, which uses an ulage valve at the base of the cylinder to control the pressure, then the valve may be leaking (simple little rubber piece to replace) or need to be adjusted.
    When there's ulage valve issues the wasted water will be spilling out onto the roof. Go outside, find the thin copper pipe sticking up from the roof, and observe if there's a wet line down the roof from this point.

    On the other hand, if it's a mains pressure hot water system there's a pressure relief valve near the top of the tank (already mentioned by another poster) The pipe from this valve should be cold. If it's hot the other end of the pipe exits outside the building, and will be spilling hot water either onto the ground, or into a drain. This becomes a job for a plumber to either replace or adjust the valve, or to reduce the input pressure.

    These valves have been a pain for me. I live very near a water treatment plant (and hence the pumps) and the water pressure fed to my house is consistently above the rated pressure for my cylinder and valve. It's not kosher, but I had to adjust the pre-set valve release point to stop it spilling water. It means my cylinder is being run at a pressure above spec, but it's survived that for 20 years. The valves can also get fouled up with deposits from the lime etc in the water.

  6. #26
    Senior Member Paul.Cov's Avatar
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    Default Re: Two of the four elements donít work properly on my stove

    The irony to piroska's correct assertion about Legionella is the new set of rules about cylinder temp and output water temps.

    Fact: If cylinders are too cool they can be a breeding ground for Legionella.
    Fact: If output temps are too high people will burn themselves.

    So new builds have to have very hot cylinders (to kill the bacteria) coupled with a system that mixes cold water with the hot water leaving the tank to bring the temps down to a safer level.

    The silly irony is that now the Legionella can find a safe existence around the output from the temperature regulated side... so we've legislated all this expensive hardware just to shift the problem a few feet further down the pipeline. There has been a documented case of infection from just this very situation.

  7. #27
    Junior Member
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    Default Re: Two of the four elements donít work properly on my stove

    Quote Originally Posted by Paul.Cov View Post
    Barry, it's screamingly obvious your hot water system is leaking somewhere. Stop fretting about the thermostat or the element, or the electrics.

    There are two very primary places to start your investigation for leaks.

    If the system is old, it's probably a low pressure (gravity feed) hot water system, which uses an ulage valve at the base of the cylinder to control the pressure, then the valve may be leaking (simple little rubber piece to replace) or need to be adjusted.
    When there's ulage valve issues the wasted water will be spilling out onto the roof. Go outside, find the thin copper pipe sticking up from the roof, and observe if there's a wet line down the roof from this point.

    On the other hand, if it's a mains pressure hot water system there's a pressure relief valve near the top of the tank (already mentioned by another poster) The pipe from this valve should be cold. If it's hot the other end of the pipe exits outside the building, and will be spilling hot water either onto the ground, or into a drain. This becomes a job for a plumber to either replace or adjust the valve, or to reduce the input pressure.

    These valves have been a pain for me. I live very near a water treatment plant (and hence the pumps) and the water pressure fed to my house is consistently above the rated pressure for my cylinder and valve. It's not kosher, but I had to adjust the pre-set valve release point to stop it spilling water. It means my cylinder is being run at a pressure above spec, but it's survived that for 20 years. The valves can also get fouled up with deposits from the lime etc in the water.
    Thanks Paul.Cov for your post.

    I just went outside and had a look at the roof and the thin pipe that sticks above it. Water is clearly running out of it through some hole and down the roof. The system is an old one. I don’t know if the hot water system is a mains pressure one or not. My guess is that it’s a low pressure (gravity feed) system.

    Would you say this hot water system has ulage valve issues? A pipe comes out the top of the cylinder then there’s something like a thread and nut out of which a pipe that goes upwards through the wood above then straight up through the ceiling to the thin pipe that sticks above the roof. The photo shows a second pipe that branches off to the right and then downwards. See photo of the area above the top of the cylinder. Click image for larger version. 

Name:	44CCAFD5-815E-4CB3-81F0-E2FF3F69EA94.jpg 
Views:	16 
Size:	48.3 KB 
ID:	10893. Sorry the photo is oriented sideways but can rotate it to point upwards if the folks in this forum want.
    Last edited by barryk; 09-05-2021 at 01:45 PM.

  8. #28
    Junior Member
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    Default Re: Two of the four elements donít work properly on my stove

    Erm, is the nut thing in my photo actually an ullage valve? See Industrial Use section in the Wikipedia article on ullage https://en.m.wikipedia.org/wiki/Ullage

  9. #29
    Old guy
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    Default Re: Two of the four elements donít work properly on my stove

    Quote Originally Posted by barryk View Post
    Erm, is the nut thing in my photo actually an ullage valve? See Industrial Use section in the Wikipedia article on ullage https://en.m.wikipedia.org/wiki/Ullage
    No it is just connecting the pipe to the tank! Stop trying to guess and employ a plumber to sort it out for you.

  10. #30
    VoidMaster
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    Default Re: Two of the four elements donít work properly on my stove

    From the looks of that pipe you have a older unfortunate layout which means that when the overflow is happening it is hot water that is lost, not cold water as could be happening if a different pipe layout was used.

    This explains your large electricity bills.

    There should be a disk shaped pressure reduction valve on the bottom of your tank and it is adjust by loosening off a lock-nut then adjusting the shaft which normally has a key-ring type circular metal ring one it at the end, small adjustments one way then the other and observing the overflow pipe will tell you when the direction is the correct one, normally half a turn will be enough to ascertain this.

    https://www.google.com/search?q=pres...x_hMDBwojUsblM
    Last edited by zqwerty; 09-05-2021 at 07:10 PM.
    It's not the least charm of a theory that it is refutable. The hundred-times-refuted theory of "free will" owes its persistence to this charm alone; some one is always appearing who feels himself strong enough to refute it - Friedrich Nietzsche

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