Noisy boiler

[CrispyFB]

We moved into our new place back in May. Pretty soon we discovered that the boiler makes a very loud "kettling" (thumping, banging) sound shortly after it has been turned on; i.e. when the temperature reaches boiling I suppose. It's right below our bedroom and I'm hypersensitive to sound so it's not a great combination. Right now it's not an issue but come winter it's going to be!

It was serviced back in March by the seller. It's a fairly old Potterton (can provide model number if needed!). There's a lot of radiators - 15 I think - if that matters.

I have a friend who is a registered plumber and her DP is a registered Corgi gas engineer. They came round, did a powerflush and a rad hammer, and fitted a filter thing to the top of the boiler that we need to clean ourselves periodically.

The boiler was mercifully silent when they left - we all assumed it was fixed!

Not to be - a week or so later and it is clanking away again just like before.

The gas engineer chap has offered to come back (obviously!) but before I call him back I'd like to see what other people might suggest so I don't feel totally bamboozled. Plumbing/boilers etc is totally outside my area of expertise, and I want to feel confident that whatever he suggests is a sensible thing to do!

Thank you!

what colour is your system filter? Do you know how to empty the dirt out?

It is possible that additional dirt has been dislodged that was not removed during the initial cleaning, and it has circulated round and collected in the boilker.

A powerflush should take a good half-day if you have 15 radiators, going round turning them on and off, reversing the flow etc.

If you have limescale in the boiler it is more difficult to remove than sludge, and the traditional removers are aggressive acids that may damage an old system. Luckily there is now a (fairly recent) mild chemical that dissolves it over time. With a modern filter you can also capture and remove the material to prevent it re-settling.

Whatever else they do, get them to show you how to empty the filter. After a clean you might need to do it once a week until the amount collected reduces; then once a month, and eventually once a year. It is quite satisfying to see the dirt that comes out reducing as your system gets cleaner. It is no harder than emptying the dirt out of a hoover, once you know how.

They showed my husband how to do it (I had to head out unfortunately for an after school club!) so I don't remember the colour. I can ask him later.

I didn't realise it might need to be done quite so frequently! The power flush definitely took most of the day, she was very thorough and was definitely turning them on and off.

We're in a very hard water area so limescale is definitely a possibility.

I'll get him to empty it this evening and see what happens. If it doesn't help maybe we should find out about the limescale remover.

Thank you very much :-)

Ask your engineers if they think that X200 and X900 would help. As I gather you have an open-vented system they are fairly easy to add. During the summer, when the radiators are off, it would be circulating round the boiler and cylinder.

Thank you very much for your excellent advice, much appreciated!

Sorry to be the bearer of gloom, but a kettling boiler is a sign that the heat exchanger is scaled up. Very difficult to remove as the exchanger is full of tiny 'fins'. When it gets scaled up water gets trapped which then boils malking the kettling noise and causing the boiler to constantly fire up and shut down to protect its self from overheating - very inefficient.

There may be a product on the market that will solve the problem, however I am not aware of one and certainly not one that might not damage the exchanger. Remember that scale maybe plugging a hole and then when you remove it you have a leak and end up needing a new boiler or heat exchanger. Retro fitting a scale reducer won't do much to help, they are designed to alter the water as it travels through the exchanger so the calcium which causes the scale does not stick.

You really need to weigh up the age of the boiler and ask is it worth spending money on it. If it's 10 + years I would say it would not be worth the expense versus the efficiencies of the new condensing boilers and a boilers average lifespan.

Thanks! It wouldn't surprise me if this was the reason. We'll probably want to upgrade the boiler one day but it's an old Potterton and from past experience (and anecdotes) it sounds like they last and last. So unless it's unsaveable I'm still willing to give scale reducer a go. If it does damage the exchanger then it's new boiler time, but given the noise is so bad from the kettling and keeping me awake it would have been new boiler time anyway if that makes sense!

Unless of course scale reducer is really expensive!!

If it is the heat exchanger and the boiler is a combi then you will get hot water intermittently (it will switch between hot and cold as the boiler fires up and then goes off). We had this problem (but not the banging noise) and we just changed the boiler in the end to a more efficient modern one. Once the heat exchanger is gone it's difficult to justify fixing it if it is an old boiler as it is a very expensive job.
At our old house we had a tank fed boiler system (it was a potterton) and we got the banging noise that you are talking about, it was loud enough to frighten me the first time as I thought somebody was breaking into the house. I can't remember what the problem was exactly, something to do with a valve, it cost us £150 to fix and that was around 7 years ago.

I picture it as an old iron Potterton. They are very simple and last a long time. If you take one apart you find the HEX is like an iron box and there is not much flow to remove any particles that collect in it, hence the banging as pockets of steam occur under the sediment.

However X900 is supposed to loosen particles so they circulate in the water, where a system filter can trap them, and X200 (formula is fairly new) somehow loosens and dissolves limescale (you do not drain either of these out). Unlike the traditional acid descalers, I think they are unlikely to do any damage. They are inexpensive chemicals at about £15-£20 each and easy to add to an open-vented system, but you must drain at least a bucket of water out before adding them. You do have to empty out the filter to remove the particles it has trapped.

Products

some reviews

Thank you very much! It sounds like it's worth a try anyway. Having just moved house the thought of dropping another few thousand on a new boiler does not appeal right at this second ;-)