Screeching from somewhere in plumbing- Megaflo?

[The OP]

The chattering noise sounds like either over pressure or over temperature problems, is there any water coming into the tundish when the noise is happening.
Plus when the noise is happening, what is actually ON on the system, is boiler burner on.

Thanks -
I'm not sure about the tundish- do you mean the gap in the pipe connected to the TPR valve? If so, then no- no water in the tundish.

When I recorded the video, nothing was on on the system- the heating and hot water had been off for several hours, and no water was being drawn anywhere in the house (intentionally, at any rate).

 

[The OP]

that sounds like a vibration on pipe caused by a faulty valve, probably stuck washer, at least i had something very similar once. Maybe its worth try to shut all valves and see if anything changes.

I know the noise stops instantly if I turn off the blue tap on the cold water inlet for the megaflo, just before the cold water combi valve. Does that tell you anything? I should add that that valve was changed a couple of weeks ago in an attempt to fix the problem, along with the 8 bar valve next to it.

What other valves should I check, do you think, and how would I do that?

 

[Rickster123]

Have you checked that you neighbour isn't having any issues??

 

[Dotty]

I know the noise stops instantly if I turn off the blue tap on the cold water inlet for the megaflo, just before the cold water combi valve. Does that tell you anything? I should add that that valve was changed a couple of weeks ago in an attempt to fix the problem, along with the 8 bar valve next to it.

What other valves should I check, do you think, and how would I do that?

In all honesty you've done as much as you can now. Get your boy back. Make sure he has his G3 qualification before he touches anything and get him to check it all over.

 

[nickelarsed]

Do you have a feed and expansion tank in the loft for your heating system?

 

[SafeGasInstall]

Must be something to do with Presure redusing valve ! Need to get plumber back to check Presure out of the balanced cold or hot water out let ? Also did they re bubble it up?

 

[PlumbBobBob]

possibly water pressure too high from mains as stan said get pressure reducing valve checked

 

[The OP]

possibly water pressure too high from mains as stan said get pressure reducing valve checked

Pressure reducing valve has been changed since all this kicked off (that was plumbers 1st guess). He even fitted a pressure gauge, but pressure never above 1.4 bar, even when noise is at its loudest. Heatrae Sadia engineer who claims noise is not coming from tank definitely regenerated the air gap. Still have the noise!

 

[The OP]

Do you have a feed and expansion tank in the loft for your heating system?

No- loft was converted, so just megaflo and a condensing boiler. No other tanks.

 

[The OP]

Have you checked that you neighbour isn't having any issues??

Not with noise, though I know for a while they couldn't get their water warm enough. all sorted now, but neighbours not sure what problem was or how remedied.

 

[The OP]

1st this is really SPOOOOKY sound .....................

what are you switching on and of on your video ?

Thats me moving the switches on the zone valves. It obv made no difference.

 

[lame plumber]

need to get an unvented cyl plumber back to tuen everything off and then isolate all the possibles one by one. also check your incoming mains pressure, sounds like you get the issue when no one is using their water supply so it could be your mains is running very high pressures, like mine does 15 bar standing pressure!

 

[The OP]

Turn the power off to your boiler tonight and see if you still get the noise.
if you do then you can rule out zone valves.
if you dont then do this for the following night too and see if there is still no noise.

Am trying this out. About 1 min after I switched off boiler at mains, the noise started, though not that loudly as only briefly. Haven't heard it since. Does this still mean I can rule out the zone valves?

 

[The OP]

In all honesty you've done as much as you can now. Get your boy back. Make sure he has his G3 qualification before he touches anything and get him to check it all over.

Sounds like good advice.

Last Q though- does the fact that closing the cold water inlet to the Megaflo (just before the pressure relief valve/cold water combi valve) causes the noise to stop instantly (and sometimes start again instantly if I open it again quick enough) tell us anything? Does that suggest the problem is occurring somewhere in the system after that inlet?

 

[lame plumber]

just get someone in, as adviced

 

[The OP]

just get someone in, as adviced

Yeah, will do. Am a bit worried about cost- noise just doesn't happen when plumbers are around, so I can foresee multiple visits if we have to make a tweak and then wait and see! Oh well.

Many thanks to all of you for your help.

 

[lame plumber]

no win no fee?

 

[The OP]

no win no fee?

Now you're talking!

 

[The OP]

I'm bumping this thread just to see if anyone has any further thoughts!

My plumber (gas safe for unvented systems) has had a good think, and consulted with colleagues, and is stumped.
He ruled out the megaflo itself (no moving parts), the zone valves and the boiler (as noise happens whether boiler on or off, even when it hasn't been on for hours).

The pressure relief and pressure reduction valves on the cold water pipe into the Megaflo were replaced after the noise started, so it's not them, unless we have had a faulty valve replaced with a faulty valve!

A shock arrestor has been fitted. And we know the noise isn't caused by increases in water pressure as the pressure stays in and around 1.4 bar. Albeit that the noise is at its worst at around 5am, at the moment.

Which leaves not much.

As the noise disappears instantly when the cold water inlet stopcock for the megaflo is closed (and doesn't happen whilst it's closed), he reckons it has something to do with the cold water system. But given that we have already spent about £600 he wants to think carefully about what to do next. Perhaps unsurprisingly, I haven't heard from him for a couple of weeks!

So- what should I do, do you think?

Many thanks!

 

[SafeGasInstall]

Disconect Megaflow for 48H and see how you get on ! Just have it bypassed and still have water at all outlets