Megaflo clunking noise, drawing hot water.

iconboy2021 · Dec 3, 2021

Hello, Hope you guys can help, I have a conk/clunk noise coming out the cylinder, when I draw hot water from any tap in the house - I’ve checked the pipes and I’m very sure its not water hammer, I will attached couple of recordings to the this post and what my setup looks like.

The cylinder is a Megaflo which is a warranty replacement from Baxi as the old one was make the same noise every minute or so whenever the boiler was heating the water, that noise was coming from within the cylinder too, some sort of expansion issue.
Baxi have been called out, and I’ve requested that they send out an senior engineer to troubleshoot this, as they have installed this unit. The noise doesn’t happen all the time and its not a loud crashing noise, its more of a metallic clunk noise however it seems more prevalent at night or when the cylinder has not been in use for a while.
I’ve regenerated the cylinder, however its made no difference, the cold water is balanced as the mains water is fed directly to the PRV and from here its and tee’ed off to the cylinder and rest f the taps. Whilst I wait for Baxi, any insights into this would be most useful, it would be sods law, to think that this unit is also faulty [like the 1st].

Thanks in advance.

iconboy2021 · Dec 6, 2021

ShaunCorbs said:
Sounds like you have high flow with the mega flows the cold inlet tube is kicked down so it’s hitting the bottom hard and either that’s your noise or it’s travelling / flowing up and vibrating the coil

thanks will show this thread to Baxi, when they come next week to have a look at it.

Chuck · Dec 6, 2021

ShaunCorbs said:
Sounds like you have high flow with the mega flows the cold inlet tube is kicked down so it’s hitting the bottom hard and either that’s your noise or it’s travelling / flowing up and vibrating the coil

Perhaps, but Megaflos claim to have an inlet diffuser to prevent this.

ShaunCorbs · Dec 6, 2021

Never seen one on the cut away models I’ve seen ?

iconboy2021 · Dec 10, 2021

Chuck said:
Perhaps, but Megaflos claim to have an inlet diffuser to prevent this.

Would a water damper valve help on the cold inlet, going in to the cylinder?

Chuck · Dec 10, 2021

iconboy2021 said:
Would a water damper valve help on the cold inlet, going in to the cylinder?

I doubt it, but I'm also not convinced that the cylinder is the root cause.

Plumbing carries sounds and I don't think you can assume that the noise originates inside the cylinder just because the emitted sound is loud near it.

iconboy2021 · Dec 11, 2021

Chuck said:
I doubt it, but I'm also not convinced that the cylinder is the root cause.

Plumbing carries sounds and I don't think you can assume that the noise originates inside the cylinder just because the emitted sound is loud near it.

thanks for your response.

The noise sounds as if its emitting from the bottom of the cylinder (where the coils are located) if its a hammer issue, then looking at this logically, the sound maybe emitting from the cold inlet, or the flow/return from - however the flow/returns are short runs - securely bolted in place - if the cold water is the culprit - then this securely fixed to the wall.

MDPE 25mm incoming downstairs directly under the eaves cupboard (1st floor) - mdpe stop valve then 22mm copper all the way to eaves - bull bore stop valve, then to megaflo blue stop valve + PRV frpm here its tee'd off the cylinder and rest of the house.

iconboy2021 · Dec 12, 2021

This seems to be getting from bad to worse, the popping noise issue - which was limited to the hot water demand from the taps, is now happening towards the end of the DHW heating cycle. A few minutes before the boiler turns off and the cylinder has achieved it's preset temperature 60° then the popping noise begins, with intervals of 1 minute apart, this carries on until the 2 port valves kicks in, along with the bypass valve. the popping noise continues for a few minutes after until the boiler stops.

Baxi popped down during the week, and sods law, I could not demonstrate the popping noise. I've sent the engineer the recordings, I will chase up with Baxi in a few days time.

I've added an edited a recording of the popping nouse, from when the boiler is heating up the water, to when the 2 port valve kicks in.

iconboy2021 · Jan 21, 2022

Hi all,

its been a while, anyways Baxi have agreed to replace & reinstall a new cylinder due to clunking + popping noise, which has got worse - the noise seem to happen randomly, even when I've not drawn any hot water or if the cylinder is not calling for hot water.

I would also like to take this opportunity to have have pipes sorted out too - can anyone recommend any optimisations?

I see that my install has a manual air bleed valve on the primary floor to cylinder cylinder, would I benefit from installing an automatic bottle type air valve and do I have too many 90° bends, would it make sense to have some of these removed.

I've also been advised to add an external expansion vessel too - perhaps this will reduce any future knocking noises too.

I welcome your thoughts.

Davetoff · May 10, 2022

Did this issue get resolved when Baxi replaced your cylinder?

iconboy2021 · May 10, 2022

Davetoff said:
Did this issue get resolved when Baxi replaced your cylinder?

I have the replacement sitting downstairs (there was delay in sourcing a new cylinder) going have some amendments made to the pipework.
I have a manual air vent on the primary flow within the cylinder, going to replace this with a Honeywell auto air vent and I'm considering a Spirovent too, also going to have an external expansion vessel installed.Once thats done, I will call out Baxi to swap out the cylinder.

Lou · Apr 12, 2024

(Just bumping a few older threads, they will drop off what is new soon)

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Megaflo clunking noise, drawing hot water.

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