Could my combi be affecting the quality of my tapwater?

Same here on a similar timescale. And my water has been run through a full spectrum water softener.

I assumed that under heat and pressure the water was 'absorbing' some sodium bicarbonate produced by the water softener and it comes out as fizzy water when the pressure drops. It only happens on my hot water - never on the cold.

All over they have lowered delivery pressures to make leaks less of a problem

I don't know really what this is. With softened water I don't have washing problems or scaling problems, just milky hot water.

Do you get microbubbles on the cold side too, or just the hot side? What about at bathroom taps?

Do you have a 'dual flow' tap, where the hot and cold water travel up different parts of the spout (usually concentric pipes) so they only mix in the air, rather than in the body of the tap? I think dual flow used to be a requirement for kitchen mixer taps but I understand that's no longer the case. Have you changed the tap recently?

Theo

I have known water supply to switch from bore hole to river and visa versa according to supply availability and treatment costs.

Perhaps it's worth asking the supplier the question about source or changes in water treatment?

in *my* case (I am not the OP), hot only, separate tap, nothing changed in 20 years.

As I said, I think its some kind of gas in solution in the *hot* water that comes out when the pressure drops

The strange thing is that the cold water doesn't display this behaviour despite coming from the same water softener.

Only in the hot water. It occurs through all the taps but I concentrated on the kitchen because all sorts of shampoos and soaps with different recipes get used in the bath and shower rooms[1] but I consistently use just one washing-up liquid there which can be considered a sort-of control.

Yes, it's a dual flow tap in the kitchen but separate hot and cold taps in the washbasins and bath.

Nick [1]I think you've prompted me to eliminate the combi from my enquiries: I can't see microbubbles in the shower water but I guess they are there because I get the same, stubborn refusal of the used, water to go down the shower waste. It's an electric shower so I guess the microbubbles are a function of heating up the mains water and are independent of the means of heating. So the question must be, what's happening to the mains water?

I think I might have to try that. I did ask someone who does water analysis if they knew if anything had changed but they say they are not taking any drinking water samples .

Thanks,

Nick

Um stupid question, as I don't have a combi, but any chance of a leak from the heating to the hot water and it is a function of the corrosion inhibitor leaking across???

As I say I have no (real) idea how a combi differs from a 'boiler' so I might be talking bolloux

Avpx

(I see the sig monster has been listening, agrees with me - it is random, I hope)

Fortunately not. Talking it over (above) made me realise I'm experiencing the same effect when using the electric shower so it's an issue with the water, not my equipment.

Nick

That's odd, I'd have thought they were required to?

While descaling my coffee machine the other day, I looked at what my supplier Severn Trent has to say about hardness, and found they publish monthly/quarterly/annual data for *many* chemicals and other properties (pH, odour, colour, turbidity etc) for my supply zone

chuck a Leicester postcode into this ...

They do say they might temporarily change the source of supply for operational reasons.

Dissolved gases coming out of solution when heated?

You could try it with a pan on the stove. Fill with cold water, gradually heat it up. Does it foam at some point before it reaches boiling point?

Maybe try the same experiment with bottled water, or water that's been pre-boiled in the kettle and then cooled, to see if there's a difference?

Bonus points if you measure the temperature it foams at with a thermometer.

Theo

With a combi the DHW and heating only "meet" on either side of a plate heat exchanger usually. If there were a leak in the PHE to allow water to cross the barrier, you would more likely see the heating side rising in pressure until the boiler tripped on over pressure since the cold main is typically higher pressure than the CH circuit.

Much the same as a normal boiler - but all the other system components in the same box, pumps, expansion vessel etc. The it typically a DHW flow sensor, a diversion valve, and a plate heat exchanger (PHE). When the boiler senses flow on the DHW, it fires the boiler (if not already on) and activates the diversion valve. This allows the pump to circulate the primary heater water only through one side of the PHE. That in turn heats the cold water flowing trough the other side from the rising main.

Except that they keep advertising it as "improved" and bringing out different variants of it.

Do people actually drink "hot" water either from a Combi boiler or via a hot water tank? I would guess that it's common practice to fill a kettle from the cold water supply, or a glass of water from the same.

Nothing to do with your combi, just deregulation of the water industry and slackening of environmental regulations. It's a Brexit Benefit. TW

Sorry, I wasn't very clear. Yes, the water companies have a legal requirement but this chap works for an environmental monitoring company but they don't have any drinking water monitoring contracts in the area - it's mainly boreholes into landfill, pollutants in proposed building sites - that sort of thing.

Interesting. I should go look at Yorkshire Water.

Nick

Please sir! Sir! Sir! May I have those bonus points, sir?

So today I have been mostly boiling water and measuring the temperatures at which certain events take place. I knew my temperature measuring probe had to be good for something[1]

I can show my workings if anybody is interested but I'm pretty sure the gas is carbon dioxide but I'm still not sure why it behaves the way that it does. I think it's CO2 because when I wave a flame over the bubbles the flame goes out but the flame stays alight over water without the bubbles.

I used three samples:[2] A- Drawn off from the tap and boiled right away B- Previously boiled and left in an open container to reach room temp C- Drawn off from the tap and left in an open container as B

A and B started to foam up at around 70deg though B was weaker in its reaction. Both cleared as the temperature went through 90deg.

What I found interesting was the reaction of C. It had been drawn off at the same time as the water which had been boiled out for sample B and both samples had been left in open containers for several hours to reach room temperature. I presume that B had absorbed more carbon dioxide from the atmosphere while it had been sitting there: that's why it foamed up again but less forcefully than when it was fresh

I presume C must have absorbed even more CO2 while it was sitting there because it started foaming just after 50deg and looked much more like a scum on the surface than the other two examples. But it wasn't a real scum, just a concentration of agitated microbubbles which disappeared when the temperature passed 90 and left no traces behind.

As suggested elsewhere in this thread, I think delving into the Yorkshire Water website is the next thing to do.

Nick [1]Other than measuring distillate fractions in a sti$%%$^&%^"... (no carrier) [2]I used others but that was more about finding out how long it would take to come to the boil

Yeah, I figured it out on reading back my own message ...

Not in The Peoples Republic of Jockistan, we still have a public owned water authority.

Are you sure it's CO2 Nick? Nitrogen would douse your flame - and there is certainly a lot of it about. Second thoughts... Nitrogen is much less soluble than CO2, so forget that.