hey guys.

we have lived in our house for 3 years now and i dont think the vailant combi boiler was that old when we moved in. it has worked fine up till now but when we turn the hot water tap on, it starts to make a sort of vibration type noise. it is then fine as soon as we turn the tap off and doesn't make the noise in any other case.

any ideas?

Here is your best bet with the problem you have

Vaillant » Service (http://www.vaillant.co.uk/installers/Service/)

Email or call. They are the only folks up to date on the system you have.

thanks mate

i am sorry to bring this thread up but vaillant haven't been bothered to respond.
as i am not under any warranty and dont have a cover plan of any sort i dont mind my father in law having a quick look as he has a basic knowledge of most building/electric/other appliances as he has always done these for work and/or his own house needs. i was hoping to be able to get at least a rough idea of what it could be to help me and him look at it.
so just to re-confirm, when i turn the hot water tap on, if it is on a decent amount, not just a trickle, it starts to make a sort of throbbing/vibrating noise that can be heard throughout the house. it doesn't happen when the central heating is on and also if the hot tap is only on low it doesn't either, only when the boiler is put under strain due to the tap being on medium to full.

cheers for any help

There could be a few causes. It could be percolating for one. Have the coils been internally cleaned of scale lately?

no mate. i apologise for sounding dumb but i dont know what any of those things you mention are but nothing has been serviced at all for at least 3 years

percolate= Many times the internal tubing/jacket will accumulate water deposits lime/scale/rust etc with the subsequent loss of water flow in the coil/tube. It causes a imbalance in the heat exchanger capability to absorb heat smoothly into the boiler water. This in turn will cause all kinds of system noise but especially when the hot water draw is at or near maximum.

The reason the term percolate is used is because it is acting somewhat like a old coffee percolator when you used to see the coffee pump to the top on the clear glass indicator and then it made the funny percolating sound.

This is fixed by isolating the coil and running a mild acid in it clearing the offending deposits. Usually this is not a job for a non professional.

thanks hvac1000.

someone who used to work on them has suggested to me that it could be either the 3 port valve not opening properly or the automatic (or something) valve not working properly.
does this sound like a possibility and any ideas if it would be something me and the father-in-law could do?

There are many possibilities but you need the knowledge to work on them. Not much do it yourself on that unit.