Been wondering why our loft has been getting so damp recently - thought it might be rain getting in but couldn't find an obvious leak in the roof and the damp on the roof lining (old Sizalkraft tar paper) is evenly spread everywhere.

Finally looked up there again this evening and there was thick fog everywhere! Looks like there's a fair amount of steam coming off the small CH expansion tank (there is a second cold water tank that supplies the power shower).

For now I've tried putting a makeshift cover on the header tank and turned the boiler thermostsat down a bit. Does the water in the expansion tank getting that hot indicate a fault? The system appears to be working normally, with all radiators getting hot (but it is very primitive, with no diverter valves so no thermostatic control over the hot water - been like that since I moved in 12 years ago)

Any suggestions?

TIA,

David.

Dave N wrote:

Does the water in the expansion tank getting that hot indicate a fault?

Yes. Only in extreme circumstances should any hot water be going up the
expansion pipe to the header tank.
In normal use, there should be no hot water going into the header tank.

Could it be the pump running too fast, and pumping the water up the
expansion pipe into the header tank? I've seen that before.

If not then you've got a problem, possibly the over-heating of the DHW.
--
Alan
To reply by mail, change '+' to 'plus'

I think you could have solved it for me!

Turned the pump up to full throttle a couple of weeks ago when the heating started kicking in because I thought one of the downstairs radiators had some sludge in it, just to see if it would heat up normally. I then left the pump running at maximum speed and forgot to turn it down again - it usually runs at the mid-setting. Oops!

Let's see how the system behaves after it's settled down again...

Many thanks!

On Tue, 25 Nov 2014 10:40:31 -0800 (PST),
wrote:

Turned the pump up to full throttle a couple of weeks ago when the
heating started kicking in ...

That doesn't help but pump over may not be a constant flow/dribble
but just a spurt when the pump starts up.

--
Cheers
Dave.

There was a steady continuous trickle of very hot water going into the header tank from the overflow pipe when I looked this evening, which I guess could happen if the pump is running flat out. My wife and I were both working from home today and it was a cold and damp day so we had the heating on for a prolonged period.

I'll take another look tomorrow after the heating has been running for an hour or two now that I've turned the pump setting down - hopefully the hot water trickle will have stopped.

On 25/11/2014 18:18, Dave N wrote:
Been wondering why our loft has been getting so damp recently -
thought it might be rain getting in but couldn't find an obvious leak
in the roof and the damp on the roof lining (old Sizalkraft tar
paper) is evenly spread everywhere.

Finally looked up there again this evening and there was thick fog
everywhere! Looks like there's a fair amount of steam coming off the
small CH expansion tank (there is a second cold water tank that
supplies the power shower).

For now I've tried putting a makeshift cover on the header tank and
turned the boiler thermostsat down a bit. Does the water in the

A lid is fine (and normal) - just make sure its not airtight

expansion tank getting that hot indicate a fault?

Nope, its doing what it is supposed to do - absorb the expansion of the
water as its heated.

The system appears
to be working normally, with all radiators getting hot (but it is
very primitive, with no diverter valves so no thermostatic control
over the hot water - been like that since I moved in 12 years ago)

Any suggestions?

Lid sounds good.



--
Cheers,

John.

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\================================================= ================/

On 25/11/2014 22:22, wrote:

There was a steady continuous trickle of very hot water going into
the header tank from the overflow pipe when I looked this evening,
which I guess could happen if the pump is running flat out. My wife
and I were both working from home today and it was a cold and damp
day so we had the heating on for a prolonged period.

ok if its coming out of the vent pipe over the top of the tank, then
that is pump over and is undesirable. It will also get the content of
the tank very hot.

I'll take another look tomorrow after the heating has been running
for an hour or two now that I've turned the pump setting down -
hopefully the hot water trickle will have stopped.

The other solution to pumpover is to convert it to a combined feed
expansion and vent configuration - where the F&E from the base of the
tank is teed into the vent pipe shortly after it leaves the main
pipework run.


--
Cheers,

John.

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\================================================= ================/

On 25/11/2014 18:30, A.Lee wrote:
Dave N wrote:

Does the water in the expansion tank getting that hot indicate a fault?

Yes. Only in extreme circumstances should any hot water be going up the
expansion pipe to the header tank.
In normal use, there should be no hot water going into the header tank.

That seems rather too "definite" a statement IMHO. The whole purpose of
a of a feed and expansion tank is to absorb the system primary water
expansion. Hence how much hot water gets into it, is more a function of
the volume of the system and then tank. Lots of rads, small header tank
will tend to also mean fairly hot header tank.

Could it be the pump running too fast, and pumping the water up the
expansion pipe into the header tank? I've seen that before.

Sure that is a possibility and far more undesirable than normal
expansion of hot water into the tank. Not least because it causes far
more condensation and also forces more oxygen into the water.

If not then you've got a problem, possibly the over-heating of the DHW.


--
Cheers,

John.

/================================================== ===============\
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|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 25/11/2014 22:30, John Rumm wrote:
On 25/11/2014 18:18, Dave N wrote:
Been wondering why our loft has been getting so damp recently -
thought it might be rain getting in but couldn't find an obvious leak
in the roof and the damp on the roof lining (old Sizalkraft tar
paper) is evenly spread everywhere.

Finally looked up there again this evening and there was thick fog
everywhere! Looks like there's a fair amount of steam coming off the
small CH expansion tank (there is a second cold water tank that
supplies the power shower).

For now I've tried putting a makeshift cover on the header tank and
turned the boiler thermostsat down a bit. Does the water in the

A lid is fine (and normal) - just make sure its not airtight

expansion tank getting that hot indicate a fault?

Nope, its doing what it is supposed to do - absorb the expansion of the
water as its heated.

The system appears
to be working normally, with all radiators getting hot (but it is
very primitive, with no diverter valves so no thermostatic control
over the hot water - been like that since I moved in 12 years ago)

Any suggestions?

Lid sounds good.



Is it possible that the pump has been installed the wrong way round? I
always understood that the pump should pump away from the expansion
pipe, i.e. it should be 'trying' to suck water down the expansion.

That was what was wrong with my in laws system - another professional
install!

Peter

On 25/11/2014 23:55, Peter Andrews wrote:
On 25/11/2014 22:30, John Rumm wrote:
On 25/11/2014 18:18, Dave N wrote:
Been wondering why our loft has been getting so damp recently -
thought it might be rain getting in but couldn't find an obvious leak
in the roof and the damp on the roof lining (old Sizalkraft tar
paper) is evenly spread everywhere.

Finally looked up there again this evening and there was thick fog
everywhere! Looks like there's a fair amount of steam coming off the
small CH expansion tank (there is a second cold water tank that
supplies the power shower).

For now I've tried putting a makeshift cover on the header tank and
turned the boiler thermostsat down a bit. Does the water in the

A lid is fine (and normal) - just make sure its not airtight

expansion tank getting that hot indicate a fault?

Nope, its doing what it is supposed to do - absorb the expansion of the
water as its heated.

The system appears
to be working normally, with all radiators getting hot (but it is
very primitive, with no diverter valves so no thermostatic control
over the hot water - been like that since I moved in 12 years ago)

Any suggestions?

Lid sounds good.



Is it possible that the pump has been installed the wrong way round? I
always understood that the pump should pump away from the expansion
pipe, i.e. it should be 'trying' to suck water down the expansion.

If you get the pump the other way round, it does not usually make it
pump over (at start up anyway[1]), but it may draw air into the system -
especially as it starts up. That in turn means lots of corrosion since
lots of fresh oxygen is being introduced all the time. (and blockages
from corrosion can cause pump over)

That was what was wrong with my in laws system - another professional
install!

Its a common arrangement that normally puts the Feed and Expansion pipe
on the suction side of the pump, so that it does not draw air into the
system, and then the vent on the output side. This does however make it
relatively easy to pump over if the vent does not pass high enough above
the high water level in the header tank before returning to the header
tank. (lots of plumbers install the vent just hooked over the top of the
tank, which means there are only a few inches of dynamic pressure
required to push water up and over the vent looping a couple of feet
above it is better)

My favoured solution is to move the vent to the suction side, but then
tee the F&E pipe into it well below the top of the vent, that way when
the pump sucks on the vent you have two pipes full of water ready to
feed into it - hopefully enough to keep the air out long enough to let
the pressure equalise.

[1] You have to be a bit careful with S plan systems to try and ensure
the pump does not end up briefly pumping against closed valves when the
call for heat is satisfied, since that can cause pumpover as the system
switches off.


--
Cheers,

John.

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| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Looks like good news - after turning the pump down from 3 to 2 and running the heating for a couple of hours this morning I've been up and checked the header tank and it's now running cool with no hot water overflowing into it.

I've rigged up a small heater and a fan up there and left the loft hatch open, which will hopefully accelerate the drying out process.

Many thanks to everyone for their advice!

David.

On Tuesday, November 25, 2014 6:31:07 PM UTC, A.Lee wrote:
Dave N wrote:

Does the water in the expansion tank getting that hot indicate a fault?

Yes. Only in extreme circumstances should any hot water be going up the
expansion pipe to the header tank.
In normal use, there should be no hot water going into the header tank.

Could it be the pump running too fast, and pumping the water up the
expansion pipe into the header tank? I've seen that before.

If not then you've got a problem, possibly the over-heating of the DHW.
--
Alan
To reply by mail, change '+' to 'plus'

Wasn`t` there a horrific accident few years ago involving hot water melting the header tank and dumping boiling contents through ceiling?

In message , Adam
Aglionby writes
On Tuesday, November 25, 2014 6:31:07 PM UTC, A.Lee wrote:
Dave N wrote:

Does the water in the expansion tank getting that hot indicate a fault?

Yes. Only in extreme circumstances should any hot water be going up the
expansion pipe to the header tank.
In normal use, there should be no hot water going into the header tank.

Could it be the pump running too fast, and pumping the water up the
expansion pipe into the header tank? I've seen that before.

If not then you've got a problem, possibly the over-heating of the DHW.
--
Alan
To reply by mail, change '+' to 'plus'

Wasn`t` there a horrific accident few years ago involving hot water
melting the header tank and dumping boiling contents through ceiling?

There was more than one case IIRC, caused by the immersion heater
thermostat failing and the water continuing to heat, going up the
expansion pipe to the cold water cistern and gradually heating up all
the water in the cold water cistern until the plastic cistern failed
(split, deformed? I don't know).

It's why all immersion heaters should have a over heat cutout as well.

So not the CH header tank, no.
--
Chris French

On 26/11/2014 12:55, Adam Aglionby wrote:
On Tuesday, November 25, 2014 6:31:07 PM UTC, A.Lee wrote:
Dave N wrote:

Does the water in the expansion tank getting that hot indicate a
fault?

Yes. Only in extreme circumstances should any hot water be going up
the expansion pipe to the header tank. In normal use, there should
be no hot water going into the header tank.

Could it be the pump running too fast, and pumping the water up
the expansion pipe into the header tank? I've seen that before.

If not then you've got a problem, possibly the over-heating of the
DHW. -- Alan To reply by mail, change '+' to 'plus'

Wasn`t` there a horrific accident few years ago involving hot water
melting the header tank and dumping boiling contents through
ceiling?

That was the main cold water cistern and a hot water cylinder boiled by
a faulty immersion IIRC. Dumped 40 gallons of scalding water onto an
elderly couple sleeping directly under it.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In message , John
Rumm writes
On 26/11/2014 12:55, Adam Aglionby wrote:
On Tuesday, November 25, 2014 6:31:07 PM UTC, A.Lee wrote:
Dave N wrote:

Does the water in the expansion tank getting that hot indicate a
fault?

Yes. Only in extreme circumstances should any hot water be going up
the expansion pipe to the header tank. In normal use, there should
be no hot water going into the header tank.

Could it be the pump running too fast, and pumping the water up
the expansion pipe into the header tank? I've seen that before.

If not then you've got a problem, possibly the over-heating of the
DHW. -- Alan To reply by mail, change '+' to 'plus'

Wasn`t` there a horrific accident few years ago involving hot water
melting the header tank and dumping boiling contents through
ceiling?

That was the main cold water cistern and a hot water cylinder boiled by
a faulty immersion IIRC. Dumped 40 gallons of scalding water onto an
elderly couple sleeping directly under it.


There have been a few cases over the years.

A 30 year old woman in 2003

http://www.telegraph.co.uk/news/ukne...d-by-boiling-w
ater-pouring-on-to-bed.html


A baby in 2006:

http://news.bbc.co.uk/1/hi/england/somerset/7179092.stm


Part of the problem seems to have been cold water cisterns that weren't
properly supported as well.
--
Chris French

On 26/11/2014 15:18, Chris French wrote:
In message , John
Rumm writes
On 26/11/2014 12:55, Adam Aglionby wrote:
On Tuesday, November 25, 2014 6:31:07 PM UTC, A.Lee wrote:
Dave N wrote:

Does the water in the expansion tank getting that hot indicate a
fault?

Yes. Only in extreme circumstances should any hot water be going up
the expansion pipe to the header tank. In normal use, there should
be no hot water going into the header tank.

Could it be the pump running too fast, and pumping the water up
the expansion pipe into the header tank? I've seen that before.

If not then you've got a problem, possibly the over-heating of the
DHW. -- Alan To reply by mail, change '+' to 'plus'

Wasn`t` there a horrific accident few years ago involving hot water
melting the header tank and dumping boiling contents through
ceiling?

That was the main cold water cistern and a hot water cylinder boiled
by a faulty immersion IIRC. Dumped 40 gallons of scalding water onto
an elderly couple sleeping directly under it.


There have been a few cases over the years.

A 30 year old woman in 2003

http://www.telegraph.co.uk/news/ukne...d-by-boiling-w
ater-pouring-on-to-bed.html


A baby in 2006:

http://news.bbc.co.uk/1/hi/england/somerset/7179092.stm


Part of the problem seems to have been cold water cisterns that weren't
properly supported as well.

Yup, either propped on joists or studwork, or often sat on a bit of loft
grade chipboard flooring, which does not maintain its integrity when
soaked.

--
Cheers,

John.

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