Tracing tiny leaks in sealed system

214 views
Skip to first unread message

visionset

unread,
Feb 16, 2007, 9:57:16 AM2/16/07
to
Okay, several months down the line I'm getting sick of filling up and
diluting the additive in my combi system.
New combi boiler in the summer, changed from vented to sealed, fair bit of
old pipework and rads. All the rad valves are new at various times within
the last 8 years. I'm guessing there are leaks at the new pressure though
nothing is visible and upstairs pipework is concealed. I suppose the leaks
are so tiny that the water evaporates on the surface making it harder to
trace. Maybe when the rads aren't on come the spring it will be more
obvious. Any one know how I can track down the source?

--
Mike W


John

unread,
Feb 16, 2007, 10:12:28 AM2/16/07
to

"visionset" <sp...@ntlworld.com> wrote in message
news:gDjBh.11822$mn2....@newsfe7-win.ntli.net...

Just a thought - is the pressure much higher than an open vented system with
a tank in the loft?

Thinking of changing mine and wondered if some of the radiators would be at
risk.


Dave Fawthrop

unread,
Feb 16, 2007, 11:02:01 AM2/16/07
to
On Fri, 16 Feb 2007 15:12:28 GMT, "John" <john.p...@ntlworld.com>
wrote:

|!
|!"visionset" <sp...@ntlworld.com> wrote in message
|!news:gDjBh.11822$mn2....@newsfe7-win.ntli.net...
|!> Okay, several months down the line I'm getting sick of filling up and
|!> diluting the additive in my combi system.
|!> New combi boiler in the summer, changed from vented to sealed, fair bit of
|!> old pipework and rads. All the rad valves are new at various times within
|!> the last 8 years. I'm guessing there are leaks at the new pressure though
|!> nothing is visible and upstairs pipework is concealed. I suppose the
|!> leaks are so tiny that the water evaporates on the surface making it
|!> harder to trace. Maybe when the rads aren't on come the spring it will be
|!> more obvious. Any one know how I can track down the source?
|!>
|!> --
|!> Mike W
|!>
|!
|!Just a thought - is the pressure much higher than an open vented system with
|!a tank in the loft?

Yes pressure goes up from less than a bar to 1-2.5 Bar

|!Thinking of changing mine and wondered if some of the radiators would be at
|!risk.

Only if they are very corroded. I used inhibitor in my radiators with the
vented system and despite having to flush out a lot of black crud, the old
radiators are fine.
--
Dave Fawthrop <dave hyphenologist co uk>
20,000 free e-books at Project Gutenberg! http://www.gutenberg.org
For Yorkshire Dialect go to www.hyphenologist.co.uk/songs/
http://www.gutenberg.org/author/John_Hartley
http://www.gutenberg.org/author/F_W_Moorman

visionset

unread,
Feb 16, 2007, 11:11:38 AM2/16/07
to

"John" <john.p...@ntlworld.com> wrote in message
news:wRjBh.7855$fa....@newsfe1-win.ntli.net...

>
>
> Just a thought - is the pressure much higher than an open vented system
> with a tank in the loft?
>
> Thinking of changing mine and wondered if some of the radiators would be
> at risk.

Yes 2 to 3 times. You hijack my thread why don't you ;-)

My experience leaves me dubious about combis (if that's what you're
planning) There is one heck of a lot to be said for keeping things simple.
Despite appearances a Combi system is much more complex, and hence
expensive, more likely to go tits up and more expensive when it does. Suits
my house, but never again. I'd say the only place for a combi is a new build
or complete renno (inc 1st fix wets) with 1 bathroom.

Does a sealant additive do what it says on the tin?

--
Mike W


Ian Stirling

unread,
Feb 16, 2007, 11:16:15 AM2/16/07
to
visionset <sp...@ntlworld.com> wrote:
> Okay, several months down the line I'm getting sick of filling up and
> diluting the additive in my combi system.

If this was a high vacuum system, I'd pump it down, connect a
mass-spectrometer, then spray helium round any suspect pipe areas.
When you get a spike of helium coming through the mass spec, you've
found a leak.

Unfortunately, this is probably not practical, unless you happen to have
a source of high vacuum, a mass spectrometer, and some way to bake out
the existing water in the piping.

visionset

unread,
Feb 16, 2007, 11:49:00 AM2/16/07
to

"Ian Stirling" <ro...@mauve.demon.co.uk> wrote in message
news:45d5d8cf$0$8744$ed26...@ptn-nntp-reader02.plus.net...

In my previous career as an analytical chemist I could of at least borrowed
a pump and sampled a makeshift port and taken in the sample to work. As a
programmer I can't think of any software I could write to help me!

--
Mike W


Message has been deleted

Adrian C

unread,
Feb 16, 2007, 1:45:14 PM2/16/07
to
Ian Stirling wrote:
> visionset <sp...@ntlworld.com> wrote:
>> Okay, several months down the line I'm getting sick of filling up and
>> diluting the additive in my combi system.
>
> If this was a high vacuum system, I'd pump it down, connect a
> mass-spectrometer, then spray helium round any suspect pipe areas.
> When you get a spike of helium coming through the mass spec, you've
> found a leak.
>

Try adding a UV dye to the water, turn the lights out and go hunting
with a UV torch.

<http://www.accepta.com/uv_leak_detector.asp>

I wonder if the stuff sold for PC modders would be OK
<http://www.wc101.com/reviews/uv-dye-green/>

--
Adrian C

Ian Stirling

unread,
Feb 16, 2007, 2:21:19 PM2/16/07
to
Adrian C <em...@here.invalid> wrote:
> Ian Stirling wrote:
>> visionset <sp...@ntlworld.com> wrote:
>>> Okay, several months down the line I'm getting sick of filling up and
>>> diluting the additive in my combi system.
>>
>> If this was a high vacuum system, I'd pump it down, connect a
>> mass-spectrometer, then spray helium round any suspect pipe areas.
>> When you get a spike of helium coming through the mass spec, you've
>> found a leak.
>>
>
> Try adding a UV dye to the water, turn the lights out and go hunting
> with a UV torch.

Or something really stinky. Ex-chemists should be good at this.

Clint Sharp

unread,
Feb 16, 2007, 3:10:22 PM2/16/07
to
In message <gDjBh.11822$mn2....@newsfe7-win.ntli.net>, visionset
<sp...@ntlworld.com> writes
Some kind of UV sensitive dye? Buy a forged note detector light, wait
until dark then follow pipework looking for glowing patches.
--
Clint Sharp

Clint Sharp

unread,
Feb 16, 2007, 3:11:37 PM2/16/07
to
In message <0glBh.19981$Da4....@newsfe6-gui.ntli.net>, visionset
<sp...@ntlworld.com> writes

>In my previous career as an analytical chemist I could of at least borrowed
>a pump and sampled a makeshift port and taken in the sample to work. As a
>programmer I can't think of any software I could write to help me!
>
Not surprised, it's a hardware problem. For a change.
--
Clint Sharp

Newshound

unread,
Feb 16, 2007, 3:22:06 PM2/16/07
to
My bet would be, as someone said above, the pressure relief valve which
normally vents outside the house. In my experience once they have lifted in
anger they seldom re-seat. Not expensive or difficult to replace, just make
sure you get the right gender on the inlet and outlet.


royb...@fsmail.net

unread,
Feb 16, 2007, 4:18:29 PM2/16/07
to

Drain the system then connect a car footpump and check with soapy
water at all the joints?

Dave

unread,
Feb 16, 2007, 5:16:32 PM2/16/07
to

Is it possible to put a food dye, or even better a fluorescent dye into
the system, turn down the temperature and leave it for a few hours
pumping water throughout the system by making heating and water demands?

My thoughts are that by reducing the temperature, you will loosen any
slack joint and enable it to leak slightly.

Then go over the pipe work looking for the dye/fluorescent marker. (A
fluorescent black light does not cost all that much. See Maplins site.)
After you find/don't find any leak, flush the system out and use as normal.

I could be wrong, but I hope this helps.

Dave

John Rumm

unread,
Feb 16, 2007, 7:18:34 PM2/16/07
to
visionset wrote:

> My experience leaves me dubious about combis (if that's what you're
> planning) There is one heck of a lot to be said for keeping things simple.
> Despite appearances a Combi system is much more complex, and hence

You seem to be confusing sealed systems with combis. Most boilers these
days use a sealed primary, not just the combis.


--
Cheers,

John.

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

John Rumm

unread,
Feb 16, 2007, 7:22:03 PM2/16/07
to

Tie a clear plastic sandwich bag round the outlet and see. If there is a
leak the bag will accumulate water.

John Stumbles

unread,
Feb 16, 2007, 8:44:07 PM2/16/07
to

If you've eliminated the PRD and are sure it really is a leak in the
pipework then go round all the rad joints feeling for damp. If you're
having to top up several times a year you may well feel dampness from the
leak even if it tends to evaporate before it can accumulate and drip off
visibly. Obviously test joints to the boiler and elsewhere also.
Compression joints are the main culprits here.

Andrew Gabriel

unread,
Feb 17, 2007, 4:40:33 PM2/17/07
to
In article <gDjBh.11822$mn2....@newsfe7-win.ntli.net>,

As you suggest, doing it when system is cold makes it much more
likely you will see the leak. Trouble is the pressure will also
be lower, leak may reduce or stop, so increase the pressure up
to the normal pressure when hot (system all turned off, obviously).
Then go around a few hours later checking all the pipework, rads,
etc for leaks. I installed a new system 5 years ago, and I've had
two of the rubber O-rings on radiator blanking plugs fail, which
I tracked this way. The leak wasn't enough that I needed to top it
up, but it annoyed me there was any leak at all. Other places to
check are the pipework inside the boiler casing, and hardest of
all, a leak in a condensing heat exchanger, because you can't
usually get to it. Check PRV isn't leaking.

To let the pressure down to normal afterwards, draw off water from
a radiator bleed valve or drain valve. Don't use the pressure relief
value as you can end up with debris stuck in it which makes it leak.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

rob...@invalid.invalid

unread,
Feb 18, 2007, 5:23:59 AM2/18/07
to
On 17 Feb 2007 21:40:33 GMT, and...@cucumber.demon.co.uk (Andrew
Gabriel) wrote:

Remember to take the plastic tops of rad valves & TRVs and check for
signs of leakage around the spindle , seepage can evaporate away
before showing up on the visible body of the valve.
Robert

Tony Williams

unread,
Feb 18, 2007, 6:44:53 AM2/18/07
to
In article <95agt29pp7bcmsmre...@4ax.com>,
<rob...@invalid.invalid> wrote:

> Remember to take the plastic tops of rad valves & TRVs and check
> for signs of leakage around the spindle , seepage can evaporate
> away before showing up on the visible body of the valve. Robert

To check rad valve spindles for leakage wrap a tissue
around each one. The tissue may not be damp at time of
checking but will generally show a telltale stain,
left behind from water that has evaporated.

--
Tony Williams.

Dave

unread,
Feb 18, 2007, 12:21:23 PM2/18/07
to
Tony Williams wrote:

And if the valve is wet, a light blue tissue will show it up better than
a white one.

Dave

Ian Stirling

unread,
Feb 18, 2007, 2:30:59 PM2/18/07
to

Toilet paper - especially cheap stuff, will shrink and crumple when it
gets a spot of water on it.

Dave

unread,
Feb 18, 2007, 3:28:12 PM2/18/07
to
Ian Stirling wrote:

That will because it is designed to dissolve in water.

Dave

visionset

unread,
Feb 18, 2007, 7:00:23 PM2/18/07
to

"visionset" <sp...@ntlworld.com> wrote in message
news:gDjBh.11822$mn2....@newsfe7-win.ntli.net...

Okay, okay, okay, but what of the Fernox Leak Sealer additive, anyone used
it? Does it do what it says?

--
Mike W


Tony Williams

unread,
Feb 19, 2007, 6:44:33 AM2/19/07
to
In article <zd6dnc1GQOq...@bt.com>,
Dave <dave...@btopenworld.com> wrote:

> Ian Stirling wrote:
> > Toilet paper - especially cheap stuff, will shrink and crumple
> > when it gets a spot of water on it.

> That will because it is designed to dissolve in water.

Arrgh! Memories of Bronco bogpaper. As scratchy as
hell, and probably even aqua regea wouldn't dissolve it.

--
Tony Williams.

brian...@synertex.co.uk

unread,
Dec 9, 2012, 7:47:07 AM12/9/12
to
Sorry to resurrect this one but I am hoping someone could shed some light on my current problem.

I have a seal combi. The pressure drops down to zero within 20 minutes of the ch going off. I fill it and we start again.

The previous tenant kept the system alive by having the fill valve constantly open, not good.

Now. I do have a leaky DHW Heat Exchanger which will fill a cup in a day.

Is this enough to explain the dramatic drops in pressure on the system ?

Thanks in advance if anyone is still around...

Toby

unread,
Dec 9, 2012, 9:12:49 AM12/9/12
to
Sounds like it might be your expansion vessel, try topping the system up to
1 bar when cold, then fire it up and watch the pressure gauge, if it hits 3
then the pressure relief valve will dump water out.

--
Toby... remove pants to reply

Roger Mills

unread,
Dec 9, 2012, 10:23:44 AM12/9/12
to
+1
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

brian...@synertex.co.uk

unread,
Dec 9, 2012, 10:44:23 AM12/9/12
to
On Sunday, December 9, 2012 2:12:49 PM UTC, Toby wrote:
Hi Toby

Thanks for replying.

I filled to 1 and it went hurtling up to 3. Then when the heating went orf it went back down to below 1

Thoughts ?

Brian

Harry Bloomfield

unread,
Dec 9, 2012, 11:29:38 AM12/9/12
to
brian...@synertex.co.uk pretended :
As the water heats up, it expands and needs somewhere to expand into -
that somewhere is an expansion vessel. Basically a tank split in half
by a diaphragm, the water below it and air pressure above it. The water
expands and pushes against the air. Either the diaphragm has burst, or
there is no air in it and it needs pressurising to 1bar - a foot pump
would do.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk


Andy Champ

unread,
Dec 9, 2012, 11:40:49 AM12/9/12
to
On 09/12/2012 15:44, brian...@synertex.co.uk wrote:
> I filled to 1 and it went hurtling up to 3. Then when the heating went orf it went back down to below 1
>
> Thoughts ?

It's the expansion vessel.

Andy

Roger Mills

unread,
Dec 9, 2012, 12:16:08 PM12/9/12
to
On 09/12/2012 15:44, brian...@synertex.co.uk wrote:

>
> Hi Toby
>
> Thanks for replying.
>
> I filled to 1 and it went hurtling up to 3. Then when the heating went orf it went back down to below 1
>
> Thoughts ?
>
> Brian

Classic symptoms of shot expansion vessel. If it's completely shot, it
will need to be replaced, but it may simply need recharging with air.

First, find the expansion vessel - a bomb-like object, probably either
close to the boiler[1] or in the airing cupboard.

Then (with the system cold) de-pressurise the water system and check the
air pressure in the expansion vessel. You should find something which
looks like a car tyre valve on the top. Use a car tyre pressure gauge.
The pressure should be 10 or 11 PSI (about 0.7 Bar). If considerably
below that, top it up. You can do this by operating a car foot pump by
hand. [If water comes out of the valve when you check the pressure, the
vessel is shot, so you'll have to replace it].

Assuming that you're able to top up the air pressure to 0.7 Bar,
re-pressurise the water system to 1 Bar, and see how you go. Hopefully,
when it then heats up, the pressure will only rise by a bit (to below 2
Bar) and won't cause the pressure relief valve to open.

[1] If it's a System Boiler, it might be inside the boiler casing - in
which case it's probably pancake-shaped rather than bomb-shaped

brian...@synertex.co.uk

unread,
Dec 9, 2012, 12:30:07 PM12/9/12
to
Cheers chaps, off I go to get a foot pump with a good guage on it. I will have to replace the DHW exhanger as its leaking anyway. I will let you know how it goes.....

Toby

unread,
Dec 9, 2012, 5:49:45 PM12/9/12
to
On 09/12/2012 15:44, brian...@synertex.co.uk wrote:
As others have already said, yes, it is the expansion vessel that is at
fault here, if I were you, I would firstly press the centre part of the
valve (Schrader valve, like you have on a car) and see what happens.

If you get air or nothing coming out, this is good, simply pump it up to
0.7 bar (10-11PSI) but do this with your system de pressurised - if when
you pump it up, you see the pressure reading on the boiler rise from 0,
then you need to let some water out of the system and then top it up
again - keep doing this until you have it at 0.7 bar, and 0 on the
boiler pressure gauge.

If, on the other hand, the Schrader valve lets out water when you press
it, then the vessel will need replacing - you can either replace like
for like, or you can just add another one to the system where
convenient, leaving the failed one connected (assuming it isn't
leaking!). - this is the best course of action if it is not easily
replaced (some boilers have the buried at the back, that required
stripping the boiler down to get to it, and some are just expensive
compared to a generic one.

An external one will look something like this, often seen in bright red too.

http://thumbs4.ebaystatic.com/d/l225/m/mIg_5OkVZrw1BUBLaBkQArQ.jpg

If you don't have one of these, then it is probably in the boiler, so
post the make and model if you cant see it in there!
--
Toby...
Remove pants to reply

Andy Champ

unread,
Dec 10, 2012, 3:40:46 PM12/10/12
to
On 09/12/2012 22:49, Toby wrote:
>
> If, on the other hand, the Schrader valve lets out water when you press
> it, then the vessel will need replacing - you can either replace like
> for like, or you can just add another one to the system where
> convenient, leaving the failed one connected (assuming it isn't leaking!).

If the schraeder valve is leaking you may be able to do something with a
metal valve cap. Like these:

<http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_564273_langId_-1_categoryId_255241>

AKA

http://tinyurl.com/boaunkw

Obviously you'll still need to fix the vessel.

Andy
Reply all
Reply to author
Forward
0 new messages