Instant vs Gas cylinder hot water

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timmmay

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#659105 20-Jul-2012 14:18

mattwnz:
timmmay: High pressure hot water cylinders last 10-15 years according to my plumber. Low pressure ones can last much longer.

Our last gas mains one lasted 40 years. The current one in the house is already 20 years old.

All I know is what my plumber told me, 10-15 years for main pressure (ie very high pressure), significantly longer for low pressure ones that have a header tank.

Jaxson

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#659115 20-Jul-2012 14:26

Elpie:
Jaxson: Yeah, you have no storage of warm water any more, so no hot water in a power cut etc if that's an issue.

Depends on the system. Some only use electricity to spark ignition and can be safely fired with one of those gas clicker thingees. I'd check with the installer to make sure this is safe with whatever system you have though! I used to safely do this with my old system but don't know how safe it is with the Infinity.

Jaxson: They come on pretty quickly once they detect flow, but can be quite noisy, so I'd think carefully about what's next to the unit. Probably not ideal if it's a bedroom etc.

If an Infinity system is noisy I'd get it checked out. Mine makes no noise at all but I guess a lot of different factors come into play with these systems.

Great points Elpie. Yes the noise of the system I have experienced was mainly ignition noise. To be sure the system sparks several times quickly. And then there is a rush of a flame as the system kicks into life and begins heating quickly. Others with a continuous pilot flame may not exhibit this behaviour.

mattwnz

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#659126 20-Jul-2012 14:35

timmmay:
mattwnz:
timmmay: High pressure hot water cylinders last 10-15 years according to my plumber. Low pressure ones can last much longer.

Our last gas mains one lasted 40 years. The current one in the house is already 20 years old.

All I know is what my plumber told me, 10-15 years for main pressure (ie very high pressure), significantly longer for low pressure ones that have a header tank.

They could have a conflict of interest though if they are trying to sell you something else. I am personally not a great fan of plumbers after problems with most of the plumbers I have used in the past.

timmmay

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#659137 20-Jul-2012 14:48

No he wasn't trying to sell me anything else, it's what he recommended, it just the usable life of them.

From this page

"Life expectancy of modern copper or stainless steel cylinders is 20-40 years, but mains pressure glass-lined steel is shorter at 12-20 years."

scuwp

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#659141 20-Jul-2012 14:51

Jaxson:
Elpie:
Jaxson: Yeah, you have no storage of warm water any more, so no hot water in a power cut etc if that's an issue.

Depends on the system. Some only use electricity to spark ignition and can be safely fired with one of those gas clicker thingees. I'd check with the installer to make sure this is safe with whatever system you have though! I used to safely do this with my old system but don't know how safe it is with the Infinity.

Jaxson: They come on pretty quickly once they detect flow, but can be quite noisy, so I'd think carefully about what's next to the unit. Probably not ideal if it's a bedroom etc.

If an Infinity system is noisy I'd get it checked out. Mine makes no noise at all but I guess a lot of different factors come into play with these systems.

Great points Elpie. Yes the noise of the system I have experienced was mainly ignition noise. To be sure the system sparks several times quickly. And then there is a rush of a flame as the system kicks into life and begins heating quickly. Others with a continuous pilot flame may not exhibit this behaviour.

Again, that comes down to being clever about where it is mounted (i.e. away from kids bedrooms etc). We have had 3 brands and all have been about the same as far as noise goes.

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cldlr76

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#659167 20-Jul-2012 15:24

Thanks for all the replies guys, lots to think about, although I have to admit I love the idea of controllers, so that is swaying me in favour of replacing the gas cylinder with instant system.
From talking to the gasfitter when he did our kitchen there is only a small amount of gas pipe that needs to be replaced, and the plumbing itself is fine.

Thanks again.

mattwnz

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#659178 20-Jul-2012 15:42

timmmay: No he wasn't trying to sell me anything else, it's what he recommended, it just the usable life of them.

From this page

"Life expectancy of modern copper or stainless steel cylinders is 20-40 years, but mains pressure glass-lined steel is shorter at 12-20 years."

You can get mains stainless steel and copper ones too which last a lot longer. The cheap ones tend to be the glass lined ones which are cheaper, so it is like everything in that you get what you pay for. It is a bit like buying a steel deck mower, versus an alloy deck mower. The steel deck ones are cheaper and don't last as long. A good stainless or copper HWC will last 40 year, which is what my old gas one was.

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Niel

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#659204 20-Jul-2012 16:15

http://en.wikipedia.org/wiki/Legionella
Keep water below 25 or above 50 degrees, but the higher the better. Remember that the thermostat temperature is at the element, not everywhere in the cylinder, so recommended to set it to at least 60. Chlorine is effective control. The issue is not with it's presence, the issue is when it grows out of control. It is only dangerous for sick/elderly people with an already weak immune system. If your cylinder is hot enough to kill all the bacteria then you don't care about the water sitting in the pipes after the cylinder.

Regarding high pressure cylinder life, on a new house if the plumber does a half decent job he will install a pressure limiter (and filter screen) on the water feed to protect the plastic water pipes and the cylinder. If he does not then he risks a warranty and potentially insurance claim. Our new house has an isolation valve and pressure limiter in the garage, in addition to the isolation valve at the water meter.

We keep our cylinder very hot as the cylinder is so well insulated the losses are so low that the increased temperature difference is not significant. The result is using less hot water to get the same temperature shower. We use the same kWh to heat less water to a higher temperature, but more people can shower with the same size cylinder. (Bad wording, it is Friday, but the logic is correct.)

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