a few pints to them that can cure it !

[tiger1050]

:wink_smile:
Hi to all
this is worth a few beers to anyone who can help and bottom this one!
Bare in mind I will answer any of your questions to the best of my ability about what I have tried/done etc as the following is not a full report.
The Back ground;
I had a central heating system that was probably getting on for aprox 20years old that came with the house when I brought it. The then system was an indirect pumped system with hot water tank and header system and always suffered with getting air in thesystem. About 5 years ago I was sick of the air bleeding routine (bathroom) and so I decided to check/ change most of the radiators for new ones. Any way this didn’t cure the problem and neither did tightening the pump fittings or slowing down the speed. So due to the age and me wanting the boiler out of the kitchen I had quotes to rip out the boiler and stick in a combi boiler. I wanted to have the total system ripped out inc pipes and rads. However 3companies inc British Gas advised that this was not needed as a pressurised system would not draw air in. Anyhow in went the new boiler (as I say about 5years ago) but from day one the air was back in the system. I called back the installers who re flushed the system and ended up scratching their heads and the only suggestion they had was to fit an automatic bleeder on the bathroom rad . This I considered was only masking the problem which goes like this


1. Re fill the system to 1.1 bar(max allowed is 1.9 bar before the safety valve will lift)
2. Get up in the morning and bleed the airout of the system and carry on with my usual day
3. Over the next three days the pressure stays at the 1.1
4. 4th day bleed the air out of the system and now the pressure falls back to the 0.8 bar where the routine starts at point 1. All over again


No water leaks have been spotted anywhere on the system. I removed and resealed the rad valves originally (this was the first cause of action)

I held a naked flame to the bleeding air some 6 years ago as someone suggested it could be gas formed by corrosion. It did not light !

I have since fitted the self bleed on the bath rad as my wife lost my “man key” for bleeding rads .... Only joking I was getting peed off with that bit so all I do is refill the system every 4 days before the boiler locks out on low pressure. My next cause of action I will hold back on and see what you experienced peeps come up with.
Thanks in advance

 

[Barry98]

His anyone checked the pressure on your expansion vessel

 

[dancinplumba]

is all pipework copper ?

 

[erpkid]

Whether you got combustion or not I would suspect corrosion if the pressure vessel checks out OK. As every time you add water you add more oxygen and the cycle begins anew. As you had an open system with potential poor pipe runs before, the sludging could have been severe so the flush or flushes may not have caught it all.

 

[AWheating]

catch the air in a small tub held upside down, then put a lighter to it, or at the air nipple if theres nothing to catch alight. if it pops/lights then its hydrogen and a sign of corrosion. Sometimes you can still get corrosion on a well flushed system causing gasing, kamco can make a special mixture of its inhibitor on request which is supposed to help against this but never seen or used it myself.

One option could be to send a water sample to fernox or sentinel for testing to atleast rule out corrosion problems.

 

[lame plumber]

was inhibitor put in you system in the first place. Have you tried a dose of system sealant (radweld type additive) to seal any pin holes in your old pipework that worked happily on tank pressure till you had it all sealed up, someone should have mentioned this when flogging you the systtem back then. And as stated get your expn vessel checked for correct operation.

 

[Avatar]

This can happen where the vent pipe is connected the wrong side of the pump.

if a combi was fitted however this should have fixed the problem . . . .

Have you had a third party check the system you have?

 

[tiger1050]

Hi All,
Thanks for the replys so far. Here with some answers so far and by all means keep the suggestions coming

1 System was flushed by the original installers of the combi boiler 3 times ( I didnt see how they carried it out mind) But not been done since
2 Yes the pipe work is all copper.
3 Expansion vessel in the boiler apears to be ok and the small bore pipe is clear ( I have checked this) and the safety valve is not venting.
4 addative was originally installed but there wont be any in there by now
5 No I havent had a third party in but I have quizzed a few
6 As in my 1st post above I did the naked flame bit and all was ok. How much is it to have the water sample tested by the way?
7 Doesnt the rad weld type stuff rely on the airobic effect ? If so wont it block the self bleed on the rad I fitted as well as the one in the boiler? or does it work different to that?

Oh one other thing to add when I top the system up I estimate its aprox a 1/2 to a full mug amount. Gut feeling tells me its a hole some where at a point where it is letting water out and air in. But a mug full every few days is a hell of a lot dont you think? I also ran the pump in summer by its self with no heat and no air entered the system. This indicated if it is a hole then its also a heat related one!
Good eh ?

Thanks again

 

[Dylan Nelson]

If they didn't replace pipework then it is definetaly incorrect laid pipe , causing air to get trapped in the system everytime u repressurise the system it will collect air from the water
Garuntee it will be this

 

[tiger1050]

Even after 3 years of constant bleeding? surely the air would come out after that amount of time?
Pipe work is underneath the floor boards notched into the joists by aprox 25mm. Main runs are in 22 and rads are taped off this in 10mm by the way.
Thanks

 

[Dylan Nelson]

It could be your vertical pipework and believe me it could trap air from the oxygen in the water every time you refill ur system. when you solve the problem and its not this simple thing let us know please. cheers

 

[stevetheplumber]

if your regularly filling the system then its leaking somewhere i assume this is now a sealed system with no tank and open vent and your filling via a loop i assume your venting because the top of the rad has gone cold

 

[tiger1050]

if your regularly filling the system then its leaking somewhere i assume this is now a sealed system with no tank and open vent and your filling via a loop i assume your venting because the top of the rad has gone cold

Hi Steve,
That is correct re sealed system etc
I would guess a leak some where one that lets water out and air in but I have had the floor boards u and cant spot anything :disappointed:

 

[Dylan Nelson]

one of your radiators could have a slight leak ! you wont notice because when the heating is on it dry's that fast, This is common probem when trying to find a leak with no water patches

 

[kay-jay]

one of your radiators could have a slight leak ! you wont notice because when the heating is on it dry's that fast, This is common probem when trying to find a leak with no water patches

Look for orange staining on valves this identifies a leak that is evaporation off when heating is on

Sent from my GT-I9100 using Tapatalk 2

 

[stevetheplumber]

some times you can feel limscale build up on the back of the pipe up to the rad run your hands down them all

 

[greyhound]

Could you confirm that it is only a 2 story house with the boiler on the ground floor. 1.1 bay will only support 30ft of water so could be pulling air in when cooling.

 

[jase158]

If it was me I would air test the system up to 2.5-3 bar (may be tricky if your safety valve pops at 1.9 bar)
if no leaks, refill system with leak sealer and see how u go.

what pressure does your boiler get up to when fully hot? must be close to 1.9 bar

 

[dhgas]

Any auto air vents fitted, and have they been checked. Have known them to pull air into a system if high enough above the boiler.

 

[tiger1050]

Thanks for the suggestions.
I havent spotted any brown marks tbh but I did find a thermo rad valve about 12mth ago with a leak. I changed that in summer but obviously the air prob persists !

Anyhow Just to let you know what I was going to try . Without getting shot down in flames....... Drain the system down. Shut off the boiler heating valves. Fill the system with compressed air and sonic leak detect the system ( we have both at work) I want to let the weather warm up so I can have the system down for a while. Will let you know how I get on. Only issue I have is deciding what pressure to take it up to. Any suggestions ?
Otherwise keep the ideas coming

 

[Sid Viscous]

Interesting thread! I usually dry test to 3 bar, but I have been known to go to 4 on systems with joints I am suspicious of! Like you say, shut the boiler valves off first!! I use a dry test guage & stirrup pump.

 

[jase158]

yeah as i said before if you go above the safety valve pressure you will never get a true reading as this will open.

Have you put a bottle under the safety valve outlet? just to see if you get anything out?

 

[tiger1050]

Sorry hadnt realised it was on the second page when I posted my last post sorry :6:
Yes its a two storey house but not a large one
Typical running pressure is aprox 0.2 -0.3 above the standing cold pressure.
No I havent put a bag on the relief valve pipe . I will anyway as a matter of course as its a easy job. Bear in mind that the problem has been here for the old boiler as well as this one though.
Air bleed is brand new on the bathroom rad and problem was there before hand
3 Bar was going to be my upper limit as well. However we have seen compressed air piped in copper in the past running at 8 bar on compression fittings !!
Thanks all again and keep them coming

 

[zeebeedee]

They left any dead legs anywhere when converting the system?

 

[Mike Jackson]

Be very wary of testing with air at high pressures, a fitting blowing off under 3 bar of air pressure can do a lot of damage to people as well as property. On no account try to tweak up a fitting if you hear it hissing, drop the pressure first in case it blows off.

 

[Sid Viscous]

Be very wary of testing with air at high pressures, a fitting blowing off under 3 bar of air pressure can do a lot of damage to people as well as property. On no account try to tweak up a fitting if you hear it hissing, drop the pressure first in case it blows off.

High pressure is subjective. Up until 2yrs ago I was installing air con for a living. We would regularly strength test an installation up to 40 bar, (that's around 600psi for you imperial boys) then soundness test to 33 bar with nitrogen. I tell you what, you know about it when a joint lets go at 40 bar!!!
Agree though, don't try & tweak anything under pressure.

 

[geminigas]

Hi All,

4 addative was originally installed but there wont be any in there by now

I would drain, refill and then add an inhibitor, and put in a leak sealer whilst you are at it. This should stop further corrosion whilst will cause gas in the system. I have been using Calchem that is an all in one inhibitor ( it can also be used with calshot leak sealer) although senitel, fernox etc all do their own makes.

 

[tiger1050]

They left any dead legs anywhere when converting the system?

Hi Zeebeedee,
Not that I am aware of. I still think its something related to the original system as the air was there then I just dint need to top it up because of the headed tank.
As soon as the weather warms up and I can take the system down I will go for a air pressuer test
Re putting the inhibiter in and sealer. my concern is I would have spent a fortune on the inhibitor at the rate of the loss/air etc. I still feeel I need to find the cause before I take the sealant as a last option?

Thanks all again

ps if I havent mentioned before then its my guess that I have to put at least a mug full of water in every 3 days . So its got to be a leak........ but its the auto bleed that is masking the air in the system dont forget

 

[kay-jay]

your auto bleed is faulty. its letting air in instead of out.

 

[AWheating]

goto agree with mike regards the air testing, it can be very dangerous. it would be safer to pressure test with water but it can make a mess. If you think about an air riffle that can cause serious injury, normally only 12-14ft lbs of pressure which is nothing compared to a bar of pressure. So a rad valve or pipe fitting poping off at 3-4 bar could cause alot of damage. As with all air testing it should be done with no persons in the property.

 

[DirksPlumbing]

goto agree with mike regards the air testing, it can be very dangerous. it would be safer to pressure test with water but it can make a mess. If you think about an air riffle that can cause serious injury, normally only 12-14ft lbs of pressure which is nothing compared to a bar of pressure. So a rad valve or pipe fitting poping off at 3-4 bar could cause alot of damage. As with all air testing it should be done with no persons in the property.

Very much agreed. Remember 7bar is enough to drive a 4" nail all the way into wood in one go.
The aforementioned 40bar are only manageable at systems with very small bores in _all_ parts of the system including the testing equipment. Do not try anything like that yourself.
And if you feel like air testing at above 1bar make sure you wear ear and eye protection.

 

[DirksPlumbing]

To the OP: my opinion would be H2O - cracking. If you have a metal bleeder you can try to ignite the air at it. But be aware the flame has temperatures around 2000degC. Do not use a lighter. Use a long match. If after ignition it sounds like a small rocket and only stops when you blow it then you know about it. You will most likely not be able to see a flame but it would relight the match again. Looks spectacular. Doing it on plastic bleeders actually too.:devil:

 

[tiger1050]

Wow !
Read my last post and I had'nt noticed how many spelling and grammer mistakes I had made !!! Just tried to edit it but couldnt find the edit button ?
Anyhow replies to the latest questions/advise and thanks again by the way.

As mentioned I have only put the auto air bleeder in the system two weeks ago. The problem has been with me for near 10 years but now getting worse.
I take your points on the testing of the system with air but I will take it up in stages and yup with the PPE. I have done refrigeration in the past also (exam in Bolton with the brazing ,soldering etc) So I get your point on what a mess it can make
Not sure about the H2o cracking thing you mention. Got any links/info etc ? Thanks

 

[DirksPlumbing]

Just wrote a long answer but this flipping backspace glitch in conjunction with the absence of a possibility to recover the last autosave just made me giving you only a quick one now.

It is an electrochemical reaction which in rare cases as well can get caused by earth faults. Reason number one is flux "contaminated" water.
A givaway is typically raised pressure in the expansion vessel. Otherwise combustion tests as described by AWheating on page 1 or myself proof it.
Water gets split in oxygen and hydrogen. The oxygen typically gets quickly turned over in corrosion. The hydrogen causes airlocks etc.