DIYnot
Local | Network
   DIYnot > Forums
Local | Network
DIYnot Network Local DIYnot Network Local  
  Forum IndexForum Index     RulesRules    HelpHelp     Join FREERegister Free     About CookiesCookies     SearchSearch     LoginLogin 

Boiler pressure dropping

This topic originated from the How to page called Problems associated with noises from the central heating system
Click here to return to the page called Problems associated with noises from the central heating system.
Goto page 1, 2  Next
 
Post new topic   Reply to topic    DIYnot.com Forum Index > Plumbing and Central Heating
Search this topic :: View previous topic :: View next topic  
Author Message
Katade

from United Kingdom

Joined: 22 Aug 2003
Posts: 6
Location: United Kingdom

PostPosted: Fri Aug 22, 2003 4:31 pm Reply with quote

The boiler in my house (Valliant) was inherited from the previous owner, hence no instructions. I have to keep on opening a valve to underneath the boiler to increase the pressure as it keeps dropping below the red line (just below 1 bar). The other day I forgot the switch the valve off and the pressure went above 3bar and the overflow was dripping (which was good), but within 3 days the pressure was below the marker. Surley this can't be right. I should not need to keep on topping up the system every week or so, should I? What could be wrong?

PS - I can't see any leaks in the house and all the rads are okay.
Back to top
 Alert Moderators

If you do not want to see this advert, click here to login or if you are new click here to join free.
breezer

from United Kingdom

Joined: 03 Jan 2003
Posts: 23328
Location: Sussex,
United Kingdom
Thanked: 27 times

PostPosted: Fri Aug 22, 2003 6:50 pm Reply with quote

sorry to state the obvious but you do have a leak somewhere. If its of any use I had the exact same problem, turned out that the drain valve (under the ground floor) was not tight, we are talking 1 drip /10 minutes but over time it was enough to cause the pressure to drop
Back to top
 Alert Moderators
Tin Gill

from United Kingdom

Joined: 16 Jul 2003
Posts: 34
Location: United Kingdom

PostPosted: Fri Aug 22, 2003 8:42 pm Reply with quote

I had a similar problem with my Vaillant combi and it turned out to be the pressure valve for the overflow that had begun to stick and so never shut properly. You mentioned that when the pressure went above 3 bar the overflow was dripping - you might want to check it's not dripping all the time.
Back to top
 Alert Moderators
Gees

from United Kingdom

Joined: 19 Apr 2003
Posts: 869
Location: Durham,
United Kingdom
Thanked: 9 times

PostPosted: Fri Aug 22, 2003 9:25 pm Reply with quote

I still have a leak somewhere.. It takes about 3 weeks to drop by abt. 1/10 of a bar. can I find it? Can I H**L.
Back to top
 Alert Moderators
COG

from United Kingdom

Joined: 13 Jun 2003
Posts: 515
Location: United Kingdom
Thanked: 1 time

PostPosted: Sat Aug 23, 2003 9:26 pm Reply with quote

Anything much more than 1/2 a bar over three months is too much, every time you top it up your adding fresh water which means more oxygen which means more corrosion. Dont expect to see a puddle of water from it is more likly a trickle from a rad valve or the PRV passing
Back to top
 Alert Moderators
ChrisR

from United Kingdom

Joined: 24 Jul 2003
Posts: 23313
Location: London,
United Kingdom
Thanked: 1053 times

PostPosted: Mon Aug 25, 2003 10:17 am Reply with quote

You won't find a leak that small probably, they tend to evaporate straight away. I'd add Leak Sealer - get it in a plumbers merchant and ask them how to get it in the system .
Back to top
 Alert Moderators
corgiman

from United Kingdom

Joined: 25 Aug 2003
Posts: 10609
Location: Surrey,
United Kingdom
Thanked: 46 times

PostPosted: Mon Aug 25, 2003 11:05 am Reply with quote

Katade wrote:
The boiler in my house (Valliant) was inherited from the previous owner, hence no instructions. I have to keep on opening a valve to underneath the boiler to increase the pressure as it keeps dropping below the red line (just below 1 bar). The other day I forgot the switch the valve off and the pressure went above 3bar and the overflow was dripping (which was good), but within 3 days the pressure was below the marker. Surley this can't be right. I should not need to keep on topping up the system every week or so, should I? What could be wrong?

PS - I can't see any leaks in the house and all the rads are okay.


my opinion is that when the system over pressurised the Pressure relief valve opened, quite correctly, but has not closed off properly. In my experiance this is due to a bit of muck in the seating and the sealing washer has corroded and needs replacing

If the pressure drop never happened before then a system leak is unlikely but it won't hurt to put some leak sealer in as ChrisR suggests
Back to top
 Alert Moderators
corgiman

from United Kingdom

Joined: 25 Aug 2003
Posts: 10609
Location: Surrey,
United Kingdom
Thanked: 46 times

PostPosted: Mon Aug 25, 2003 11:08 am Reply with quote

I think the problem is that when the system over presuurised the Pressure Relief Valve opened, quite rightly, but has failed to close off correctly due to a bit of muck or the sealing washer being corroded.

if the drop never happened before then a system leak is very unlikely but it won't hurt to inject some leak sealer in as ChrisR suggests
Back to top
 Alert Moderators
pb

from United Kingdom

Joined: 08 Dec 2003
Posts: 3
Location: United Kingdom

PostPosted: Mon Dec 08, 2003 12:17 pm Reply with quote

I have a similar problem but cannot find any visible leak site. Does anyone have any views on one possible explantion:-

There is at least one location where a leak would not be visible/obvious. If general hot water tank (HWT) is also heated by the boiler CH circuit then there could be a leak in the loop passing through the HWT. The direction of leak would of course be from hi to lo pressure. Thus, if the CH circuit is at higher pressure than HWT then water will leak (unseen) into the hot water tank until p difference is zero.

A clue as to whether this explanation is valid would be to check the pressure to which the boiler CH circuit levels out to following topping-up from main. If that roughly equates to the pressure head in the HWT circuit then maybe the leak is within the CH circuit where it passes through the HWT. One bar of pressure is approx equivalent to 30 foot head of water.

Incidentally, does any one know why the Vaillant Instruction Manual warns that " No inhibitors must be added to the C.H. system"? Surely that would only be tenable for the ideal situation of a system that is perfectly sealed and thus the supply of oxygen limited?
Back to top
 Alert Moderators
jcb

from United Kingdom

Joined: 10 Mar 2004
Posts: 3
Location: United Kingdom

PostPosted: Wed Mar 10, 2004 8:19 am Reply with quote

I am also having a problem with a pressure drop about .2bar per day, it is coming from the pressure release valve. Is it just a matter of replacing the valve or could there be another cause???
Back to top
 Alert Moderators
Galileo2004

from United Kingdom

Joined: 12 Mar 2004
Posts: 1
Location: United Kingdom

PostPosted: Fri Mar 12, 2004 12:40 pm Reply with quote

Same problems here with my Worcester Heat Systems Combi. I have now turned off all the radiators (valves off at both ends), put more water in so that the pressure returns to 1bar and will wait to see if the pressure drops back to zero again (which normally takes 2-3 days).

The pressure release valve may be dripping, but its hard to determine when its raining outside.

Does anyone have any other suggestions on where to find the leak?
Back to top
 Alert Moderators
murphytanya

from United States of America

Joined: 29 Sep 2009
Posts: 1
Location: Washington,
United States of America

PostPosted: Tue Sep 29, 2009 5:02 pm Reply with quote

The pressure at my boiler drops below 1 bar (it takes about 2 weeks to drop to 1/2 bar). I do see a visible leak at the top of the expansion tank that is hooked up to the boiler. Would a leak in this location be causing the pressure drop? I was told by a plumber that it would not, since the flow of water from the boiler to the radiant heat system doesn't pass by the expansion tank. Any thoughts?
Back to top
 Alert Moderators
buck51

from United Kingdom

Joined: 15 Feb 2008
Posts: 842
Location: Manchester,
United Kingdom
Thanked: 92 times

PostPosted: Tue Sep 29, 2009 5:14 pm Reply with quote

Why do you think, pb, jcb, & Galileo2004, did not get a response???
Start your own post this one died twice 2003 & 2004 then you may get a beter response than they did.
Back to top
 Alert Moderators
findaleak

from United Kingdom

Joined: 13 Dec 2009
Posts: 1
Location: London,
United Kingdom

PostPosted: Fri Mar 05, 2010 4:40 pm Reply with quote

Hi Everyone

If you have leaks you cannot locate, check out findaleak.co.uk they are the central heating leak gurus !!

Cheers
Back to top
 Alert Moderators
corgiman

from United Kingdom

Joined: 25 Aug 2003
Posts: 10609
Location: Surrey,
United Kingdom
Thanked: 46 times

PostPosted: Wed Jun 02, 2010 8:07 pm Reply with quote

spam spam spam

wonderful spam

icon_smile.gif
Back to top
 Alert Moderators
Search this topic :: View previous topic :: View next topic  
Post new topic   Reply to topic    DIYnot.com Forum Index > Plumbing and Central Heating All times are GMT
Goto page 1, 2  Next
Page 1 of 2

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
Similar Topics   Replies   Views   Posted 
Baxi Boiler pressure dropping error E119 3 3500 Wed Jan 13, 2010 8:26 am
Pressure dropping on combi boiler 4 960 Wed Sep 14, 2005 1:26 pm
Boiler dropping pressure. 4 500 Sun May 25, 2008 6:55 pm
boiler pressure dropping after new rad added 5 80 Fri Aug 23, 2013 9:48 pm
Boiler pressure dropping daily! 6 100 Tue Aug 20, 2013 12:51 pm


 
DIYnot
Find an Expert | Find a Supplier | Search DIYnot.com
Network | Advertising | Newsletter
DIY | DIY How To | @home | DIY Wiki | DIY Forum
By using this site you agree to our Terms of Service / Disclaimer.
Please read our Privacy Policy. Copyright © 2000-2014 DIYnot Limited.