I have noticed that the noise is mainly made first thing in the morning and last thing in the evening.
Is this symptomatic of the valve please?
If it was the water would it be more consistently happening?
Can I adjust the valve myself?

I personally think your system sounds ok, the added leak sealer is most likely the cause and also the engineer not wanting to get his hands dirty. As a few have said its most likely a boiler a fault as it really doesn't sound dirty.

As for power flush, in theses times I'm offering choices,

1 mains flush etc at est cost, but on flushing if we feel requires a flush we will offer it but not free of charge and all blame is shifted to customer

2 power flush from start at est cost


Note on early post of power flush at £380 that sounds very cheap, going rate is between £500-750 here depending on system and engineer

You mentioned that you didn't get the installer to fix the leak, did he offer! Why not?

How long after the install was the leak sealer put in?

I think we need all the facts before we Slag off the installer

I had a new boiler, vailant ecotec 415 in August 11. Had a chemical flush & magnaclean as part of installation and on day of installation.
Boiler now making funny noise.
Vailant engineer says the water in the system is dirty, possibly too much inhibitor? it's a soft of pale yellow colour and they won't do anything until it is much cleaner.
Original installer says we now need to have a power flush (£380 + Vat).
Is this correct or am I being taken for a ride please? By either engineer?
Are there any other options?
Thank you for any help.

Read more: http://www.diynot.com/forums/plumbing/am-i-being-ripped-off-powerflush-realy-necessary.313752/#ixzz1nK8PyjIg

sorry iv not read other response to your question but i hope this helps a bit.
1.boiler noise can be caused by a number of things including poor water, having said that yellow water should not cause boiler noise (the science is that poor water in your system is basically your radiators that rot and then the particals fall into the bottom of your rads (black sludge), some of these particals will be suspended in the water, now depending on your system type, sealed/ non-sealed , combi / system boiler depends on what happens to the suspended particals. normally on a combi the particles reattach them self to the water parts of the boiler forming a hard black scale (not lime scale) on the insides this damages pumps, divertor valves, sensors ,flow switches dryfire stats and in heat exchangers stops the heat transfer that then causes kettleing.on a system boiler the particals will also form on the cold feed slowly blocking it and there for the flow rate around the boiler and radiators. theres alot more to it than this but this gives you a idea)
2.yellow water can be cuased by some chemicals (a straw yellow) or by a over use of flux thats not been cleaned out of the system after instalation. if its flux theres a good chance that you will also get air in your rads, but it wont be air it will be hydrogen form a chemical reaction between the flux and metals in your c/heating.
3.£380 for a flush? this is a good price if its done correct (with chemicals and a powerflush machine). Not sure it would need it mind you, powerflushes are to remove sludes and part blockages not yellow water. if theres any sludge particals floating they should be caught in the magnaclean (if its been installed right) its worth checking the magnet in there (follow the manufactures instructions that came with the magnaclean or you will get wet).the question of weather you or the installer should pay for this flushing if required is a matter between you vaillant say in there installer instructions

3.15 Cleanser and inhibitor
In the case of an existing installation, it is ESSENTIAL
that prior to installing the new boiler the system
is thoroughly flushed. For optimum performance
after installation of a new system, the boiler and its
associated central heating system should also be
flushed. Flushing should be carried out in accordance
with BS7593: 1992 using a cleanser such as Sentinel
X300 or X400, or Fernox Superfloc.
For long-term corrosion protection, after flushing, an
inhibitor suitable for stainless steel heat exchangers
should be used, refer to the current issue of BS 5449
and BS 7593 on the use of inhibitors in central heating
systems. Examples are Sentinel X100 and Fernox.

the key word is "thoroughly flushed" and depends on opinion of the engneer. for what its worth the way i look at is , if i take a radiator off and theres black sludge in it when i tip the last few inchs of water out it needs a (or if more than the last few inchs is black) "powerflush" NOT chemical flush. Also if you have fitted a new boiler to old radiators (15 years plus )that where on a open vented system (the type of system that has two square header tanks in the loft one big tank and one small tank and a hot water cylinder) theres a good chance it needed a POWERflush (but not always)

Many thanks for all your help.
I am still unsure quite what to do next though.

Call group service (Vaillant) tell them to get back out and show them this thread. As long as you've been truthful I can't see them taking much of a stance to be fair. If they charge you, say to them well if it's a boiler fault I'll charge for my time off work, we can all play the manufacturer game. Either that or threaten to get an independent in, if his report is boiler issue send them a large bill with compensation attached. But beware, if all is not as you've stated they will have you over a barrell.

Big note though make sure they take water out of YOUR system and not a pre made bottle hiding in the van

I have emailed Vaillant direct with a link to this thread asking for their help.

That'll do it

I have scanned thru the 4 pages of this post and I would say mickyg is right for 3 reasons
1 he knows vaillants

2 the 400 series of vaillants often have this "drifting" of co2 %

3 I've never know "slightly yellow" water to cause a problem


I would ask you installer to call round with his analyser and check it out with adjustments it will take about 10 minutes to do and will probably solve the issue