You mentioned you recently had some work done, does any of this work coincide with when the problem started? One of my associates suggested this can also be caused by an outlet drawing more hot water than can be supplied to the cylinder cold fill.
There are four things that happened prior to or around the time this new noise started appearing:
1) we got a new washing machine
2) dishwasher pump started failing now doesn't work at all
2) i actually forgot we had another awful vibrating noise from about June until October. I could never work out where it was from until I found a video of the noise. It wasn't every day but got alot more frequent. It happened between 3-5am and lasted several seconds. I found a video of the same noise.
View: https://youtu.be/zZg7MDp06dI
(not my video but this happened for shorter period of time)
I bled the radiators last month and found one which was full of air and the noise has not been back for a month since I did this.
3) boiler vibrated for the 1st time around the time this new mystery vibration noise started appearing. Again I don't have a video of it as it is completely random and very infrequent. It has done it now 3 times in two months or as far as I am aware. Had a boiler service 2 weeks ago everything seemed fine with it but it did make the noise. Engineer said it could be 1 of 4 things, tested it bit more and it didn't do it again. It has done it once since so going to get the heating engineer to have another look at it.
View: https://youtu.be/IUT8aNDXExs
again not my boiler but same thing. It has done it 3 times in 2 months and I'm at home all the time so unless it does it when I'm sleeping I'm confident its not frequent.
Does this give any more insight into the problem?
Are we just really unlucky to have separate issues or are they all somehow related?
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Can you provide a couple of photographs of the pipework around the expansion tank please?
Has someone competent checked the expansion tank is sound and correctly charged?
If you stop the boiler from heating the unvented tank and let it cool down does the effect still occur with cold water? I think the answer is probably 'yes' based on what you've said already.
It doesn't sound like 'water hammer' to me. More like the sort of slip-stick friction you get when central heating pipes expand due to the passage of hot water. If I'm right, one possibility is the reduction of pressure due to opening the tap is causing the pipework to move. E.g. when you pressurise an elbow it straightens slightly and when you depressurise it returns to it's correct shape. This would be more plausible with plastic pipework than with copper.
If it is due to thermal expansion, it would explain your observation that once its happened, opening taps within 30 minutes results in less of an effect.
Yes I got it all serviced last week by a company who only deals with unvented systems
Can you provide a couple of photographs of the pipework around the expansion tank please?
Has someone competent checked the expansion tank is sound and correctly charged?
If you stop the boiler from heating the unvented tank and let it cool down does the effect still occur with cold water? I think the answer is probably 'yes' based on what you've said already.
It doesn't sound like 'water hammer' to me. More like the sort of slip-stick friction you get when central heating pipes expand due to the passage of hot water. If I'm right, one possibility is the reduction of pressure due to opening the tap is causing the pipework to move. E.g. when you pressurise an elbow it straightens slightly and when you depressurise it returns to it's correct shape. This would be more plausible with plastic pipework than with copper.
If it is due to thermal expansion, it would explain your observation that once its happened, opening taps within 30 minutes results in less of an effect.
Yes it had a full service last week no issues found. Prv was replaced this week even though it looked fine - made no difference.
So I only heat my water twice a day morning and evening for a hour. It will do it regardless of whether it is heating up or has been off 5 hours. We don't notice the noise again after the first instance until the water has been heated in the evening. I tested it with the kitchen hot tap yesterday as normally it would be the bath or shower ran first so we thought it was only related to the bathroom. The noise occurred with the kitchen tap as well so seems like any hot water tap.
If it was a water hammer do they occur everytime a tap is opened or can it be infrequent? If it was to do with thermal expansion is this problem able to be fixed?
I've provided more info above about another two issues which could be related? One seemed to resolve when I bled the radiators. The other has occurred infrequently 3 times over the past 2 months.
Can you provide a couple of photographs of the pipework around the expansion tank please?
Has someone competent checked the expansion tank is sound and correctly charged?
If you stop the boiler from heating the unvented tank and let it cool down does the effect still occur with cold water? I think the answer is probably 'yes' based on what you've said already.
It doesn't sound like 'water hammer' to me. More like the sort of slip-stick friction you get when central heating pipes expand due to the passage of hot water. If I'm right, one possibility is the reduction of pressure due to opening the tap is causing the pipework to move. E.g. when you pressurise an elbow it straightens slightly and when you depressurise it returns to it's correct shape. This would be more plausible with plastic pipework than with copper.
If it is due to thermal expansion, it would explain your observation that once its happened, opening taps within 30 minutes results in less of an effect.
Yes specialist company dealing with unvented cylinders has serviced it last week. No issues identified. Replaced PRV even though no visible faults but didn't work.
Yes it will happen if the water is cold. I only heat twice a day for an hour atm. So if I turn tap on after its been heated but isn't actually on it will do it. After that it either won't do it or to a lesser degree more times than not I don't hear it again until I've heated the water for a 2nd time and then put the hot water tap on. I thought it was just the bathroom taps but its not as it did it with the kitchen hot water tap last night too.
I have added couple bits of extra info/videos about other issues that could be related in the post above. I'd actually forgotten about the noise earlier in the year as not heard it since I bled the radiators a month ago.
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After saying the boiler vibration was infrequent it just happened as we stood in the kitchen. Boiler had just fired up as the hot water programme had literally come on when it happened. The video doesn't show how loud it is and unfortunately only caught a little bit of it as it was over in seconds again. No fault code on the boiler. Vibration from white vessel occurred as normal when hot water tap turned on.
