We've had a combi-boiler fitted, early this year, to drive the heating
and hot water. It seems to be working fine at the moment. The thing
is though that the hot water comes out white and it takes a few
seconds in the sink before it clears.

I know it's only miniscule air bubbles in the water and that they're
harmless in themselves. The question is, what is causing the bubbles
to be present in the water and is it inticative of any possible
problems in the system?

I've had a good check around over the last few weeks and can't find
any sign of leakage.

Thinking about it (though it's probably unconnected) - the central
heating does not have a header tank but is fed from the mains via a
valve. I check the central heating pressure periodically and let more
water in if the pressure drops. The thing is, the pressure does drop
so I'm having to allow a bit more water in every month. Doesn't sound
right to me but I still can't find any leaks anywhere.

Any advice on the significance (if any) of the white water or central
heating pressure drop gratefully received.

Thanks,
Vince.

On Tue, 19 Aug 2003 00:53:01 -0700, Vince wrote:
We've had a combi-boiler fitted, early this year, to drive the heating
and hot water. It seems to be working fine at the moment. The thing
is though that the hot water comes out white and it takes a few
seconds in the sink before it clears.

Thinking about it (though it's probably unconnected) - the central
heating does not have a header tank but is fed from the mains via a
valve. I check the central heating pressure periodically and let more
water in if the pressure drops. The thing is, the pressure does drop
so I'm having to allow a bit more water in every month. Doesn't sound
right to me but I still can't find any leaks anywhere.

Just wanted to let you know that I'm having exactly the same two symptoms.
Hadn't worried about it until now! :-)

Didn't know if you wanted to know that you weren't alone!

Cheers,


ANdy

Andy Jeffries wrote:
On Tue, 19 Aug 2003 00:53:01 -0700, Vince wrote:

We've had a combi-boiler fitted, early this year, to drive the heating
and hot water. It seems to be working fine at the moment. The thing
is though that the hot water comes out white and it takes a few
seconds in the sink before it clears.

Thinking about it (though it's probably unconnected) - the central
heating does not have a header tank but is fed from the mains via a
valve. I check the central heating pressure periodically and let more
water in if the pressure drops. The thing is, the pressure does drop
so I'm having to allow a bit more water in every month. Doesn't sound
right to me but I still can't find any leaks anywhere.


Just wanted to let you know that I'm having exactly the same two symptoms.
Hadn't worried about it until now! :-)

Didn't know if you wanted to know that you weren't alone!

Cheers,


ANdy

Make that three of us :-)

I don't worry about the white these days - it's a lot less noticeable
now the boiler is working properly at last and I can get a high
throughput instead of a pathetic dribble out of it. Lower flow rates
with a high temp just starting to form seems to be the time that the
white shows up. I've wondered if it is scale that forms inside from the
last cycle being broken free in minute particles when the boiler heats
for the current HW demand, but putting it into a glass the water soon
becomes clear so I don't think it can be that.

Both combi's I've had have had slow leak symptoms, but I rent, so I'm
not going to pull up all the floorboards to check the rad pipes. I just
top it up every so often (the new boiler is a lot less prone to this) -
and also, given the filling loop is permanently connected, I wonder if
it is going back through there despite a check valve.

I don't worry about either - I don't drink the hot water, so that's not
an issue, and the pressure drop in the heating circuit is so small as to
be negligible. One thing to consider is if you run the heating very hot
the pressure may build up and the boiler vent slightly on it's pressure
relief valve, mine's custom settable by the boiler engineers - or maybe
a slow leak through the valve. Looking at the vent pipe may indicate if
this is the case.

Velvet

In message , BillR
writes
Vince wrote:
We've had a combi-boiler fitted, early this year, to drive the heating
and hot water. It seems to be working fine at the moment. The thing
is though that the hot water comes out white and it takes a few
seconds in the sink before it clears.

I check the central heating pressure periodically and let more
water in if the pressure drops. The thing is, the pressure does drop
so I'm having to allow a bit more water in every month. Doesn't sound
right to me but I still can't find any leaks anywhere.

I don't think the pressure drop is anything to do with the "white" water.
The pressure drop is concerned with the CH (radiator) side of the system and
is due to a small leak/seepage from the radiator circuit and should be
fixed

An alternative possibility (though less likely given a newish boiler))
is a small leak via the diaphragm in the pressure vessel.

As you say the white water could just be the heat driving out the normal
dissolved air in the incoming water but I would have thought the water would
have had to be much hotter than is normal for a domestic HW tap.

I've seen something similar.
--
Chris French, Leeds

In article ,
Velvet writes:
Andy Jeffries wrote:
On Tue, 19 Aug 2003 00:53:01 -0700, Vince wrote:

Thinking about it (though it's probably unconnected) - the central
heating does not have a header tank but is fed from the mains via a
valve. I check the central heating pressure periodically and let more
water in if the pressure drops. The thing is, the pressure does drop
so I'm having to allow a bit more water in every month. Doesn't sound
right to me but I still can't find any leaks anywhere.

Just wanted to let you know that I'm having exactly the same two symptoms.
Hadn't worried about it until now! :-)

Didn't know if you wanted to know that you weren't alone!

Make that three of us :-)

When I installed central heating, I installed full bore
isolation valves on the various branches. Partly, this was
so I could isolate parts of the system to easily rule it
out of any such leak, but also it was because I installed
it slowly over a few years and wanted to be able to use
parts of the system when other parts were incomplete.

Both combi's I've had have had slow leak symptoms, but I rent, so I'm
not going to pull up all the floorboards to check the rad pipes. I just

You should inform the agent or owner. They might decide to
have it repaired rather than fixing dry rot in a few years
time. When I rented many years ago, my contract said failure
to report obvious faults like this left me liable for
consequential damages.

--
Andrew Gabriel

Andrew Gabriel wrote:

In article ,
Velvet writes:

Andy Jeffries wrote:

On Tue, 19 Aug 2003 00:53:01 -0700, Vince wrote:


Thinking about it (though it's probably unconnected) - the central
heating does not have a header tank but is fed from the mains via a
valve. I check the central heating pressure periodically and let more
water in if the pressure drops. The thing is, the pressure does drop
so I'm having to allow a bit more water in every month. Doesn't sound
right to me but I still can't find any leaks anywhere.

Just wanted to let you know that I'm having exactly the same two symptoms.
Hadn't worried about it until now! :-)

Didn't know if you wanted to know that you weren't alone!

Make that three of us :-)


When I installed central heating, I installed full bore
isolation valves on the various branches. Partly, this was
so I could isolate parts of the system to easily rule it
out of any such leak, but also it was because I installed
it slowly over a few years and wanted to be able to use
parts of the system when other parts were incomplete.


Both combi's I've had have had slow leak symptoms, but I rent, so I'm
not going to pull up all the floorboards to check the rad pipes. I just


You should inform the agent or owner. They might decide to
have it repaired rather than fixing dry rot in a few years
time. When I rented many years ago, my contract said failure
to report obvious faults like this left me liable for
consequential damages.


It's not leaking anywhere near enough, and I pointed it out to the
engineer who sorted the boiler after it was incorrectly installed.
Haven't had to top up since then, so am presuming he did something that
stopped it. I've been here coming up to 11 years now - told the
original landlord, he wasn't concerned, at that point was topping up the
boiler maybe once every few months, it would stabilise at about 1.25
bar, but not sit at 1.5 for months on end (which is how the system was
set when I moved in). New boiler runs closer to 1.75, drops only very
very very slowly, requires much much less topping up, which would
suggest the rad pipework is sound. Boiler bloke pressured the system
higher than 2 initially to check for leaks, nothing obvious then either.

Velvet

"BillR" wrote in message ...
Vince wrote:
We've had a combi-boiler fitted, early this year, to drive the heating
and hot water. It seems to be working fine at the moment. The thing
is though that the hot water comes out white and it takes a few
seconds in the sink before it clears.

I know it's only miniscule air bubbles in the water and that they're
harmless in themselves. The question is, what is causing the bubbles
to be present in the water and is it inticative of any possible
problems in the system?

I've had a good check around over the last few weeks and can't find
any sign of leakage.

Thinking about it (though it's probably unconnected) - the central
heating does not have a header tank but is fed from the mains via a
valve. I check the central heating pressure periodically and let more
water in if the pressure drops. The thing is, the pressure does drop
so I'm having to allow a bit more water in every month. Doesn't sound
right to me but I still can't find any leaks anywhere.

Any advice on the significance (if any) of the white water or central
heating pressure drop gratefully received.
I don't think the pressure drop is anything to do with the "white" water.
The pressure drop is concerned with the CH (radiator) side of the system and
is due to a small leak/seepage from the radiator circuit and should be
fixed. Fernox do a leak sealer in a tube that can easily be injected into a
rad bleed valve. This has worked well for me on two different systems but
its not cheap.
As you say the white water could just be the heat driving out the normal
dissolved air in the incoming water but I would have thought the water would
have had to be much hotter than is normal for a domestic HW tap.

The white bubbles in combi hot water is exactly this - dissolved air
being driven out. It's just because the water has been recently heated
from cold water rich in dissolved gas (air? oxygen?) without any time
sitting around in a tank for the bubbles to come to the surface. If
you heat a kettle of water, you can see the disolved gas coming out of
solution long before boiling point.

Vince wrote:

We've had a combi-boiler fitted, early this year, to drive the heating
and hot water. It seems to be working fine at the moment. The thing
is though that the hot water comes out white and it takes a few
seconds in the sink before it clears.

I know it's only miniscule air bubbles in the water and that they're
harmless in themselves. The question is, what is causing the bubbles
to be present in the water and is it inticative of any possible
problems in the system?

I've had a good check around over the last few weeks and can't find
any sign of leakage.

Thinking about it (though it's probably unconnected) - the central
heating does not have a header tank but is fed from the mains via a
valve. I check the central heating pressure periodically and let more
water in if the pressure drops. The thing is, the pressure does drop
so I'm having to allow a bit more water in every month. Doesn't sound
right to me but I still can't find any leaks anywhere.

Any advice on the significance (if any) of the white water or central
heating pressure drop gratefully received.


The tiny bubble are dissolved gas in the water coming out of solution.
This _may_ mean that HW temperture is too hot

As for topping up see the FAQ.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

"MarkM" wrote in message
om...
"BillR" wrote in message
...
Vince wrote:
We've had a combi-boiler fitted, early this year, to drive the heating
and hot water. It seems to be working fine at the moment. The thing
is though that the hot water comes out white and it takes a few
seconds in the sink before it clears.

I know it's only miniscule air bubbles in the water and that they're
harmless in themselves. The question is, what is causing the bubbles
to be present in the water and is it inticative of any possible
problems in the system?

I've had a good check around over the last few weeks and can't find
any sign of leakage.

Thinking about it (though it's probably unconnected) - the central
heating does not have a header tank but is fed from the mains via a
valve. I check the central heating pressure periodically and let more
water in if the pressure drops. The thing is, the pressure does drop
so I'm having to allow a bit more water in every month. Doesn't sound
right to me but I still can't find any leaks anywhere.

Any advice on the significance (if any) of the white water or central
heating pressure drop gratefully received.
I don't think the pressure drop is anything to do with the "white"
water.
The pressure drop is concerned with the CH (radiator) side of the system
and
is due to a small leak/seepage from the radiator circuit and should be
fixed. Fernox do a leak sealer in a tube that can easily be injected
into a
rad bleed valve. This has worked well for me on two different systems
but
its not cheap.
As you say the white water could just be the heat driving out the normal
dissolved air in the incoming water but I would have thought the water
would
have had to be much hotter than is normal for a domestic HW tap.

The white bubbles in combi hot water is exactly this - dissolved air
being driven out. It's just because the water has been recently heated
from cold water rich in dissolved gas (air? oxygen?) without any time
sitting around in a tank for the bubbles to come to the surface. If
you heat a kettle of water, you can see the disolved gas coming out of
solution long before boiling point.

You can see this with some taps, especially aerated taps.


---
--

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(Vince) wrote in message . com...
...the hot water comes out white...

I check the central heating pressure periodically and let more
water in if the pressure drops. The thing is, the pressure does drop
so I'm having to allow a bit more water in every month.

Thanks for all your answers. I'm much reassured. I'll not worry
about the white water any more but keep an eye on the CH pressure.

Vince.