INTERMITTENT WATER PRESSURE LOSS

[John Taylor]

Re: Domestic c/h with Vaillant ecoTEC plus 837 boiler.

For the past 12 months or so, boiler water pressure has intermittently dropped from the normal operating pressure of 1.8bar to 0.3bar overnight, indicated by fault code F75.

I would re-pressurise the system and monitor pressure for a couple of weeks noting stable pressure then forget about it. A couple of months later, I would wake up to no-heat and/ or no-DHW and re-pressurise again. About the 3rd occassion I called out my local installer/service engineer and advised him that there had not been any slow reduction in water pressure. He did a visual search but could not find water leak.

The Vaillant service engineer was then called out and replaced faulty water pressure sensor which was 'gunged up'.

2 weeks later, same problem, woke up to no heat, water pressure at 0.3bar, code F22 this time. My local installer called out, visual search for water leak, none found. I then agreed to him adding C-Tec Miracle Seal to the system. The product information states that it is "100% guaranteed not to clog the system in accordance with application instructions."

However I have a radiator with TRV set for frost protection, which, by coincidence, won't now heat up when TVR operated to call for heat. I have checked for air-lock and bled the rad, no air or aerated water released, just lots of clear water........no sign of the coloured sealant nor sealing of the 'leaking' bleed valve!.

Before calling out my service engineer again, I am hoping this forum's experts could help with my queries viz:-

Q1 - Does anyone know of a case where adding the leak sealant can cause problems?.

Q2 - Why hasn't the sealant 'sealed' the bleed valve?.

Q3 - What is the likely reason for the rad not heating up ?.

Q4 - What other causes of loss of water pressure in Vaillant boilers are regularly recorded?.

Looking forward to your responses....many thanks.

 

[Riley]

Leak sealant is always last resort for me. I’ve heard of and seen no end of problems with blocked AAVs and weak pumps as a result. There were other things that the Vaillant engineer should have checked before leaving which could’ve contributed to your pressure loss. Sadly they are within the boiler and so you’ll need a gas safe engineer to look. Could be a blockage or a part that needs some attention. If you disconnect the radiator does water come out of the offending TRV. If not I’d say the leak sealant has fubar’d it

 

[John Taylor]

Thank you Riley for your prompt reply.

Both the Vaillant service engineer and my Vaillant approved installer checked the boiler internals for water leaks prior to their remedies.

Referring back to my O.P., I have just thought of a another question.

Q5 - What would cause water pressure to drop from 1.8bar to 0.3 bar instantly overnight resulting in the 'low water pressure' code F22 to register?.

Please note that, at no time, during the occasions of my monitoring the water pressure, did I log a slow, progressive drop.

 

[Rob Foster]

Re: Domestic c/h with Vaillant ecoTEC plus 837 boiler.

For the past 12 months or so, boiler water pressure has intermittently dropped from the normal operating pressure of 1.8bar to 0.3bar overnight, indicated by fault code F75.

I would re-pressurise the system and monitor pressure for a couple of weeks noting stable pressure then forget about it. A couple of months later, I would wake up to no-heat and/ or no-DHW and re-pressurise again. About the 3rd occassion I called out my local installer/service engineer and advised him that there had not been any slow reduction in water pressure. He did a visual search but could not find water leak.

The Vaillant service engineer was then called out and replaced faulty water pressure sensor which was 'gunged up'.

2 weeks later, same problem, woke up to no heat, water pressure at 0.3bar, code F22 this time. My local installer called out, visual search for water leak, none found. I then agreed to him adding C-Tec Miracle Seal to the system. The product information states that it is "100% guaranteed not to clog the system in accordance with application instructions."

However I have a radiator with TRV set for frost protection, which, by coincidence, won't now heat up when TVR operated to call for heat. I have checked for air-lock and bled the rad, no air or aerated water released, just lots of clear water....no sign of the coloured sealant nor sealing of the 'leaking' bleed valve!.

Before calling out my service engineer again, I am hoping this forum's experts could help with my queries viz:-

Q1 - Does anyone know of a case where adding the leak sealant can cause problems?.

Q2 - Why hasn't the sealant 'sealed' the bleed valve?.

Q3 - What is the likely reason for the rad not heating up ?.

Q4 - What other causes of loss of water pressure in Vaillant boilers are regularly recorded?.

Looking forward to your responses....many thanks.

Leak sealer is really not right, some water pathways in the boiler are tighter than your leak and the gunge just gives the boiler a premature heart attack
Rob Foster aka centralheatking

 

[Riley]

If they are genuinely proper installers then they will tell you that there is not nevessarily A visual internal leak. And I am very surprised that they’ve not tested the relevant parts in order to check this

 

[Scott_D]

Check all rads for leaks when hot and cold.
Put a balloon or clear bag over the external pressure relief pipe.

 

[Rob Foster]

If they are genuinely proper installers then they will tell you that there is not nevessarily A visual internal leak. And I am very surprised that they’ve not tested the relevant parts in order to check this

Top Up Mate from Flowflex cures the problems with invisible leaks on pressurised systems Rob Foster aka centralheatking

 

[Riley]

Top Up Mate from Flowflex cures the problems with invisible leaks on pressurised systems Rob Foster aka centralheatking

Rob there is every chance that it’s a part in the boiler that has not been properly tested and is causing the boiler to cough out. This product will just mask the problem

 

[John Taylor]

Is that in addition to Miracle Seal already used?.

 

[Riley]

Miracle seal should’ve been the absolute last place they went in terms of a repair. It sounds like a very lazy engineer to me

 

[John Taylor]

Hi Riley, What does 'cough out' mean?... my guess would be excess water pressure relief-valve opens!. For my Vaillent would this be greater than 3bar and if so, how/why would the pressure rise to that level?.

PS - Doh!, I can't work out how to insert quotes. Other forums I use have a different routine. Please can someone instruct me through the correct key strokes.

 

[rpm]

Bottom R/H corner of post you want to quote.

 

[Riley]

Yes cough out is the PrV opening and there are likely reasons why

 

[Old Account]

Can definitely agree with Riley here. Perhaps they never checked the parts properly and therefore leading to a quick pressure loss. It’s always difficult to locate a leak like this as it can be anywhere and everywhere. But as many engineers have suggested above all the obvious things should be checked first.

 

[John Taylor]

UPDATES:
1. Re: Water pressure loss - no further incidents since Miracle Seal added to circuit.

2. Re: Conservatory radiator not heating up - My C/H service engineer on holiday abroad returned my telephone call and advised me to remove TRV thermostat unit and check movement of valve spinal having given it a spray of WD40.

Followed advice, spindle ok but still no heat.

Back to basics ("turn it off, turn it on", as the PC tech guy would say ), so I checked the lock shield valve, noted it was only partially open, as set 10 years previously, and opened it little more. Yappa dabba do, instant heat. Monitored TRV activity, room temp control back to normal.

I assume that the lock shield was open at the minimal position for normal water flow and therefore the Miracle Seal actually blocked off the flow. I can't think of any other explanation.

It's now fingers crossed, hopefully no more low water pressure alerts.

Meanwhile thanks to everyone for their advice.

 

[John Taylor]

UPDATE 2 - Received email from forum helpdesk as to my status and forum inactivity so here I am . Being a general member of the public, activity only related to specific problems so I have pleasure in providing the following update:

No heating again 15th February 2019. Water pressure low, re-pressurised and everything OK since then i.e. no further pressure loss shutdowns & no detectable water leaks. I have monitored/logged the water pressure daily since then so up to today it is steady at 2/2.1 bar when ON and 1.7/8bar when OFF.

The cause of the problem, being intermittent, remains a mystery!. I can only assume it is a spurious 'sensor' error?. My installer/ service engineer is also puzzled .

However my annual boiler service is due mid May so in the meantime any other feedback would be very welcome.

 

[Riley]

Thank you for the update

 

[John Taylor]

UPDATE 2 - Received email from forum helpdesk as to my status and forum inactivity so here I am . Being a general member of the public, activity only related to specific problems so I have pleasure in providing the following update:

No heating again 15th February 2019. Water pressure low, re-pressurised and everything OK since then i.e. no further pressure loss shutdowns & no detectable water leaks. I have monitored/logged the water pressure daily since then so up to today it is steady at 2/2.1 bar when ON and 1.7/8bar when OFF.

The cause of the problem, being intermittent, remains a mystery!. I can only assume it is a spurious 'sensor' error?. My installer/ service engineer is also puzzled .

However my annual boiler service is due mid May so in the meantime any other feedback would be very welcome.

Thank you for the update

You're very welcome.

 

[Harvest Fields]

 

[Welder]

spray of WD40.

FYI. Never ever spray a spindle with WD40. It's a hydrocarbon based fluid which WILL attack the nirtile or EPDM o-ring the spindle relies upon for sealing. A spring sits behind it so it should pop out. Using something flat you should be able to push it down if its a little stuck. If you can't then simply change it.
ALL TRVs should, like isolation valves, be 'exercised' at least annually to keep the o-ring lubricated and to stop it sticking prematurely.

 

[Rob Foster]

FYI. Never ever spray a spindle with WD40. It's a hydrocarbon based fluid which WILL attack the nirtile or EPDM o-ring the spindle relies upon for sealing. A spring sits behind it so it should pop out. Using something flat you should be able to push it down if its a little stuck. If you can't then simply change it.
ALL TRVs should, like isolation valves, be 'exercised' at least annually to keep the o-ring lubricated and to stop it sticking prematurely.

thank you Yd your info is great
fings what u never knew but do
now because of UKPF ..chking

 

[Harvest Fields]

thank you Yd your info is great
fings what u never knew but do
now because of UKPF ..chking

What’s has happened to the spelling mate?

 

[Welder]

What’s has happened to the spelling mate?

That was your 'street' speak wasn't it Rob?

 

[Aire]

Your intermittent problem may be caused by your system pressure been set to high. 1.7/8 bar Is too much. Drop your pressure so its reading just over 1 bar when the system is cold.

 

[chris watkins]

I have monitored/logged the water pressure daily since then so up to today it is steady at 2/2.1 bar when ON and 1.7/8bar when OFF.

Hi John,
So your highest radiator / part of heating system is over 10 Metre's above your boiler then ? Your service engineer will need to drain the boiler to check & adjust the vessel charge next service.
(Beat me to it Craig.)
Just to correct you F75 is not loss of system pressure that is the F22 you had the second time.

 

[John Taylor]

Hi John,
So your highest radiator / part of heating system is over 10 Metre's above your boiler then ? Your service engineer will need to drain the boiler to check & adjust the vessel charge next service.
(Beat me to it Craig.)
Just to correct you F75 is not loss of system pressure that is the F22 you had the second time.

Thanks very much for your advice Craig and Chris. The highest rad is 1.5 metre above the boiler so I will drop the water pressure to 1.1bar as recommended by you and confirmed by my referral to the Vaillant Installation booklet. I am surprised that neither the Vailliant or my service engineer set the water pressure at about 1.1bar nor stressed that I must do the same when I needed to re-pressurise the system.

I was therefore responsible for filling the system until I saw the LED reading reach 1.8bar, well below the max of 3bar...amateur DIY experts, what should you do with them?

Re: your reference to my first registered fault code of F75 and water pressure reading [LPW] of 0.3bar, I had checked the manual's troubleshooting table for F75 which stated the following:
"Fault, no pressure change detection when starting pump - Cause: Water pressure sensor and/or pump defective, air in installation, too low water pressure in boiler; check adjustable by-pass, connect external expansion vessel to return." so I assumed LWP was the cause. As previously posted, a Vaillant service engineer visited and changed a gunged-up water pressure sensor but as you can see, since then, the problem persists.

By reducing the water pressure to 1.1bar, is it likely that the intermittent low pressure shutdowns will stop? and/or what are the other possible causes?.

 

[chris watkins]

No, there are other underlining issue that a proper boiler engineer needs to correct / investigate when on site. Unfortunately not all the problems can be fixed by reading the Manufactures Instructions albeit that if some plumbers did at least have a thumb through they might have a better understanding of the issues.
F75 is the boiler looking for a change in the standing pressure when it starts up.