Is there a difference in water from a kettle and combi boiler?

BarryH

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Never realised I should have tried harder with my chemistry lessons at school so I'll ask on here, is there a difference in water boiled in a kettle and hot water coming from a combi boiler?

I'd just like to know which would be best or better way of getting warm water for weekly changes.
 

Siege

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Boiled water will boil of the kh (temporary hardness) I think.

So best to use the combi boiler.

That’s as far as my science goes!:lol:
 

Parablennius

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Funny you ask this just now. I pretty much know the usual, low TDS of my tap water. Recently when preparing change water I used the combi to warm and the TDS was "indicating" higher than the supply water!! I have no idea what went on but water gained TDS at the hot tap. There will be an explanation, no doubt. from someone better qualified than me. Whatever, I use the kettle now.
 

Zeus.

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Well the water from the kettle will be hotter than the combi boiler OFC if it has just boiled so as Siege says its temporary hardness will be removed so boiled water is better for making ferts up as it will be softer and will hold more ferts in solution before it is saturated with the ferts.

So in theory water from the kettle is better for your tank if after reducing the hardness of your tank, but in practice the thought of boiling and cooling enough water for a nano tank isnt worth it IMO and for my 500l tank would take too long and using an RO unit would probably be cheaper/better/faster if after softer water and mix it with tap water to suit your needs.

Recently when preparing change water I used the combi to warm and the TDS was "indicating" higher than the supply water!! I have no idea what went on but water gained TDS at the hot tap.

Probably due to the water being hot as it changes the conductivity of the water and not all TDS pens allow for the temp difference and even those that do may not be that accurate, if you let the water cool to room temp and compare it with water from the cold tap that has also reached room temp they should be the about the same, although the water from the hot tap sample may be sightly softer depending on how hot the bioler heats the water as it may remove a little of the temporary hardness.

I use RO or distilled water for making ferts
Tap water for WC in High tech tanks 500l and 50L.
Have been experimenting with RO water in my small Low tech tanks as I have hard/very hard water
 

Parablennius

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Well the water from the kettle will be hotter than the combi boiler OFC if it has just boiled so as Siege says its temporary hardness will be removed so boiled water is better for making ferts up as it will be softer and will hold more ferts in solution before it is saturated with the ferts.

So in theory water from the kettle is better for your tank if after reducing the hardness of your tank, but in practice the thought of boiling and cooling enough water for a nano tank isnt worth it IMO and for my 500l tank would take too long and using an RO unit would probably be cheaper/better/faster if after softer water and mix it with tap water to suit your needs.
Agreed, but my tap is usually around GH3, KH1.5 so not much carbonates to shift.

Probably due to the water being hot as it changes the conductivity of the water and not all TDS pens allow for the temp difference and even those that do may not be that accurate, if you let the water cool to room temp and compare it with water from the cold tap that has also reached room temp they should be the about the same, although the water from the hot tap sample may be sightly softer depending on how hot the bioler heats the water as it may remove a little of the temporary hardness
Also agreed the temp diff. could be the reason. I'll pay more attention next time, it was merely a casual observation at the time.
 

dw1305

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Hi all,
I have no idea what went on but water gained TDS at the hot tap.
Probably due to the water being hot as it changes the conductivity of the water and not all TDS pens allow for the temp difference and even those that do may not be that accurate, if you let the water cool to room temp and compare it with water from the cold tap that has also reached room temp they should be the about the same, although the water from the hot tap sample may be sightly softer depending on how hot the bioler heats the water as it may remove a little of the temporary hardness.
It is literally just that, the water is warmer.
Siege says its temporary hardness will be removed
It will, but you have to pour off the boiling water and then continually strain the water as it cools, otherwise he solid CaCO3 scale will go back into solution as the water cools and picks up atmospheric gases.

cheers Darrel
 

Thumper

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Boiled water will boil of the kh (temporary hardness) I think.
If you use the steam. Otherwise the KH actually raises as just H2O boils off.

Furthermore, if you heat up water you could have an issue concerning O2.
The warmer the water, the less O2 is dissolvable. If you heat the water up tooo fast your fish could get a gas bubble disease.
 

zozo

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It kinda depends on, what is meant with the term boiler. And it actually doesn't boil the water but only heats it preferably bellow 60°C. Since at this temperature, the calcium (CaCO3) starts to deposit in the kettle and pipes.

Anyway there are different types of water boilers in use. The stand-alone electric or gas boiler type that heats a kettle with X volume and keeps this at a constant set temperature. Made for the benefit, since the water is constantly preheated, we will have about immediately warm water from the tap. Till the darn thing runs empty after a bath. And then you have to wait for it, at least an hour again.

These types of boilers are running out of popularity because of it uses quite a lot of energy to keep the water to the set temperature all day long. Also with this constant heating, there still will be quite some CaCO3 deposite in the kettle. Water coming from this type of boiler could be coming out softer than it came in. This is due to the erratic temperatures in the kettle if it's a stagnant system. The burner is under the kettle and the temp sensor somewhere at the top. Before the top is 60°C the lower part might be 80°C for a while. And if its heated long enough without tapipng any water from it only more CaCO3 will deposite.


The instantaneous heaters, have a constant flow through at a set temperature bellow 60°C

I know there are combinations, actually instantaneous heaters with a small build in boiler kettle maybe 5 or 10 litres. This also to give warm water sooner than a instantaneous heater without a boiler/kettle from the same era. And only have to constantly preheat a small amount of water. But i believe nowadays these boiler combinations are not very much in use anymore. Because they were very prone to CaCO3 damage in the small kettle and internal 3-way valves in a rather short period. And since its such a small kettle, it will change to instantaneous heating after taking 5 litres of warm water. This will have little to no impact on water parameters.

Nowadays the (Turbo) heat exchange technique and material use is much more evolved and the Central Heating / Warm water devices are about all instantaneous heaters.

And in common terms, it might still be named a central heating/water boiler combination. But it has little to do with an actual boiler/kettle as we knew it from a few decades ago.
 
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BarryH

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I mentioned in the first post that it was a "Combi Boiler" which may be the same as you mention "And in common terms, it might still be named a central heating/water boiler combination".
 

zozo

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There once was a time that the term boiler stood exclusively for a heater kettle. Even in my country, the English term Boiler was used for that. Than is somebody said i have a Boiler we knew a water heater kettle was meant. Nowadays this term and since the popular energy awareness the technique is no longer in use very much and a combi is simply heating instantaneously with the help of a 3-way valve the moment you ask warm water from the tap.

I can imagine since the boiler is an English word for a water heater/cooker and no matter how it does the job it still is a boiler in UK terms. But that i actually do not know.

A look inside the combi device will probably reveal if it still contains a kettle. And even if so it will be too small to change water parameters if more volume is asked from the tap than the kettle contains. :) Because than it switches over to instantaneous heating. With too little time and not hot enough to change anything in the water.

And then it depends on the water contents if it changes or not. Water is not simply water.
 
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