Boiling Water

[ericmark]

I have started a thread in plumbing section asking the question, should I get new taps fitted in my mothers house? What I can't understand is if the water from a combi is not potable, then where would you ever use a kitchen mixer tap as shown

as with electric either special tap, or storage tank, and just can't think of any application where that tap could be used, even in the bathroom I drink water from sink. So why would any manufacturer make those taps if the water from combi is not potable?

 

[JohnW2]

I thought you were just meaning that you had already said that as it wasn't really an answer. You said "suppose" and "could".

Ah, I see. I used "suppose" and "could" really as a CYA measure (given that there are interrogators and cross-examiners around), since I do not know the precise official requirements for water to be regarded as 'potable'.

However, despite the 'suppose/could' pre-emtion of interrogation, I am as sure as makes no difference that what I said was correct. I was responding to a comment suggesting that water which had been heat-treated ('pasteurised') ought to be 'potable' - but was pointing out that there are (non-microbiological) contaminants that would not be destroyed by moderate heating (or even boiling) that clearly would render water 'non-potability' - e.g. unacceptable levels of heavy metals (arsenic, lead etc.).

Kind Regards, John

 

[EFLImpudence]

Yes, but that was my question.

The water going into a combi IS potable.
So, if the water coming out is NOT, then the combi must be doing something to the water.

It's not really anything to do with the heating.

 

[ericmark]

Yes, but that was my question.

The water going into a combi IS potable.
So, if the water coming out is NOT, then the combi must be doing something to the water.

It's not really anything to do with the heating.

If water is hot it is more likely to leach out chemicals from plastic pipes or copper pipes using lead solder than cold, however if this is really a risk, then why are the mixer taps today as shown in my diagram?

 

[EFLImpudence]

I have a plastic electric kettle.

 

[davelx]

If water is hot it is more likely to leach out chemicals from plastic pipes or copper pipes using lead solder than cold, however if this is really a risk, then why are the mixer taps today as shown in my diagram?

With a combi, I would be very surprised if the hot water that you use to make a drink has been hot in the pipes long enough to pick up even a small trace of anything from the pipes. I would think that the (now cold) water that had been sitting in the pipes will have been well and truly flushed by the time the water is hot enough to be worth using to reduce the kettle boiling time, and the hot water will be flowing at quite a high rate, so I would be surprised to see that it had picked up any significant contamination in the short time it's been hot in the pipe. Add to the that fact that most metallic hot water pipes have a thin layer of scale isolating the pipe from the water.

if anyone knows of any research into this I'd be interested to read it.

 

[JohnW2]

The water going into a combi IS potable. So, if the water coming out is NOT, then the combi must be doing something to the water. It's not really anything to do with the heating.

Exactly. If you look back (I daren't quote myself, since I then seem to get told off!) you will see that that's exactly what I said - that if the "something the combi was doing" was adding traces of metallic elements, minerals or other non-biological contaminants, then heat treatment would 'not make it any safer'.

However, I will say, yet again, on the basis of informed common sense (and without any 'evidence or proof'), that it remains my personal belief that a few seconds (at most) in a combi's heat exchanger is not going to introduce any significant amount of (non-microbiological) contamination into the water.

Kind Regards, John

 

[EFLImpudence]

Alright. I suppose what I am really asking is "IS it not potable"?

It seems we've had this before, but I don't remember.
https://www.diynot.com/diy/threads/is-it-safe-to-drink-hot-water-from-a-combi-boiler.479202/

On the other hand - some nonsense from the US.
https://www.politico.eu/article/britains-youth-voted-remain-leave-eu-brexit-referendum-stats/

 

[DetlefSchmitz]

If you search for it, the internet is full of people asking this question. No question or answer ever quotes any regulation. Of course in the UK, one was always told not to drink from the hot tap, for reasons dating originally back to the Romans. Most people asking the question seem to be basing it on what their parents once told them. I haven't noticed BAS, who seemed to make the original assertion, providing any factual evidence or quoting any regulations, so I draw my own conclusion.

 

[JohnW2]

Alright. I suppose what I am really asking is "IS it not potable"?

As I've said, I do not know the precise official/legal/regulatory definition of 'potable' (which is simply Latin for 'drinkable) water. However, I have found this on-line ...

The law requires that drinking water is wholesome and clean. It sets down maximum acceptable concentrations for a number of potential contaminants. In addition, there is a general clause, which requires:
“Water is free from any micro-organisms and parasites and from any substances which, in numbers or concentrations, constitute a potential danger to human health.”

... which leads me to what I keep saying - that, assuming that the incoming water does (as it should) satisfy the above criteria/'requirements', then (on the basis of informed common sense, and without any 'evidence or proof'), i do not personally believe that a few seconds (at most) in a combi's heat exchanger is going to introduce a sufficiently significant amount of contamination into the water to cause it to change such as to no longer satisfying the above criteria/'requirements'.

As has been said, if someone is suggesting that water which is boiled after being heated by a combi is 'regarded as non-potable', then I think it is really for them, not anyone else, to produce 'evidence and proof'. However, even if such 'evidence and proof' could be provided, that would not alter the fact that, personally speaking, I would still be happy to drink such water and/or use it for cooking.

Kind Regards, John

 

[davelx]

If you search for it, the internet is full of people asking this question. No question or answer ever quotes any regulation. Of course in the UK, one was always told not to drink from the hot tap, for reasons dating originally back to the Romans. Most people asking the question seem to be basing it on what their parents once told them. I haven't noticed BAS, who seemed to make the original assertion, providing any factual evidence or quoting any regulations, so I draw my own conclusion.

Well, when I was young I was told not to drink from the hot tap (gravity fed from tank in the loft as was the norm in "them days") in our house. When I was old enough to venture into the loft, I found the cold water tank, which was uncovered and contained the skeleton of a bird. I never drank water from the hot tap in that house!

So maybe we don't have to look back to the Romans

 

[JohnW2]

Well, when I was young I was told not to drink from the hot tap (gravity fed from tank in the loft as was the norm in "them days") in our house. When I was old enough to venture into the loft, I found the cold water tank, which was uncovered and contained the skeleton of a bird. I never drank water from the hot tap in that house!

... nor, I imagine, cold water from the storage tank!

One problem 'back then' was that, at least in some areas, it was theoretically 'not allowed' to have mains-fed cold water taps anywhere other than in a kitchen. That meant that it was very common for bathroom taps to be fed from the cold water storage tank - so, undesirable though it was (for reasons such as you describe) many people were 'drinking' that stored water, at least when cleaning their teeth - but sometimes more extensively.

Of course, quite apart from the fact that many properties no longer have cold water storage tanks, even when they do the current regulations require all sorts of measures (not the lest of which is a lid) to reduce the risk of dead birds, rats or bugs finding their way into the tank!

Kind Regards, John

 

[AlanE]

Interesting thread really, seeing as I spent the last few years of my working life repairing boilers and plumbing systems in general. Certainly some strange myths, theories and conclusions drawn in this thread.

Is combi water drinkable? Why not Potable water enters boiler flows through, normally, a plate heat exchanger and a sensor to detect water flow. No way the system water can mix unless this decides to become defective with pinholes. Same water comes out so wht not drinkable?

Other modern device used is an unvented cylinder. Again sealed from the enviroment.

Hot water is 'made unsafe' because fittings had been soldered with lead solder. Consider the amount of 'free solder' from this source and compare it with the exposure from having their water main constructed of lead. How many people have suffered lead poisoning from this route? Lead water main is considered low risk by virtue of an oxide layer that has formed isolating water from the lead pipe.

Disturbe this lead pipe and it could damage this formed oxide coating. That is the official view. In the real world what would happen - at one point all these pipes were new and unlined?

The Continent, and many other countries decided to opt for sealed domestic water systems whereas the UK went the other way and supplied the entire household water supply, bar the kitchen tap, from a local water tank in the loft.

Originally this tank, which fed all the households other taps, was open topped. Sometimes made of galvanised steel, which rusts, an asbestos one which contains fibres hareful to health and then plastic ones. All in their day were often open and all manner of 'things' were attracted to them. Common downside was low water pressure from non mains fed taps.

At one time hot water sealed galvanised, rustable. tanks with a 'porthole inspection cover' on them. They were replaced with copper cylinders. However both types have an expansion pipe that ran over the cold water storage tank and it was no unknown to tutn on hot tap and a dead spider appear!

Where is the water allowed to mix in a mixer tap? If you have a gravity, tank fed, system then it must mix at the tap outlet or have a check vakve in the hot supply. Reason being cold water would have high pressure compared to that of the hot causing mains pressure to push babk up to loft tank and it could overflow. Another problem with gravity fed hot water it would need vary careful adjustment of the cold tap to get any semblance of 'warm' water.

Modern combi, or vnvented cylinders, pressure id vertually the same so this problem doesn't exist.

 

[JohnW2]

Is combi water drinkable? Why not Potable water enters boiler flows through, normally, a plate heat exchanger and a sensor to detect water flow. No way the system water can mix unless this decides to become defective with pinholes. Same water comes out so wht not drinkable?

You would have to ask the person who said that the water coming out of a combi "is not regarded as potable". However, as I said, if that really is an official view (which I somewhat doubt) it seems to be OTT, since, as I've said, the chance of any significant (heavy metal or whatever) contamination getting into the water during its very brief passage through the heat exchanger would surely be incredibly small.

Hot water is 'made unsafe' because fittings had been soldered with lead solder. Consider the amount of 'free solder' from this source and compare it with the exposure from having their water main constructed of lead. How many people have suffered lead poisoning from this route?

Quite so. I spent the first 20 or so years of my life in a house which was plumbed entirely in lead, and I have yet to become aware of any consequential harm!

Originally this tank, which fed all the households other taps, was open topped. Sometimes made of galvanised steel, which rusts, an asbestos one which contains fibres hareful to health and then plastic ones. All in their day were often open and all manner of 'things' were attracted to them. ... At one time hot water sealed galvanised, rustable. tanks with a 'porthole inspection cover' on them. They were replaced with copper cylinders. However both types have an expansion pipe that ran over the cold water storage tank and it was no unknown to tutn on hot tap and a dead spider appear!

Yep, throughout those first ~20 years of my life, I was also exposed to both hot and cold rusty tanks (and dead spiders!), just as you describe - and, again, I seem to have survived the experience.

Where is the water allowed to mix in a mixer tap? If you have a gravity, tank fed, system then it must mix at the tap outlet or have a check vakve in the hot supply. Reason being cold water would have high pressure compared to that of the hot causing mains pressure to push babk up to loft tank and it could overflow.

As I wrote above, that is certainly the case with kitchen mixer taps fed by mains cold water and gravity-fed hot water. However, since traditionally both hot and cold water to taps other than in a kitchen were gravity fed, it used to be the case (and quite probably still is) that 'bathroom mixer taps' often/usually have the mixing done a fair distance upstream of the 'outlet' (end of spout), mixed water being fed into the 'spout'.

Kind Regards, John

 

[ban-all-sheds]

It seems everyone has forgotten, or is deciding to ignore, the fact that I said "My understanding is that hot water from a combi is not officially potable", not "Hot water from a combi is not officially potable", and later followed up with "if I'm right", and "I could be wrong".