Water hammer noises and heat pump

Getting some weird random noises.

Octopus engineer came out replaced some pipework earlier this week. Now the water hammer is back.

I put the power heating on for the hot water and noises happened few moments later.

This is the chart

Similar noise


Air? (info code being shown on heat meter?)

Control valves plumbed in backwards anywhere?


We get the same with DHW - it sounds as if there’s a lot of vibration from the coil in the DHW tank.

Because of our build we use all of the cheap rate night electricity for the UFH. We have a massive slab and a very energy efficient build - so we actually don’t use the ASHP for DHW, we simply have the diverter set up to schedule a boost during the cheap rate electricity period.

The reading I did indicated that it could be dynamic vibration which is to do with the way the water flows through the pipes and is affected by the bends etc. We don’t get this vibration in the UFH buffer tank, only in the DHW tank. They are from the same manufacturer but are different sizes and coil configurations. The UFH buffer tank has 2 coils which are connected serially. The DHW tank has one. They are both corrugated coils - I did wonder if this might be an issue.

I had an email conversation with the manufacturer but they weren’t interested in helping and the ASHP folks were equally uninterested - understandably as the tanks were already installed before we got them to quote for the ASHP.

One solution in one of the papers I read about dynamic vibration was to vary the flow rate. This obviously isn’t something you can do from the ASHP controls, so the suggestion was to put in a bypass with a gate valve, to be able to vary the flow through the tank coil. So a bit of trial and error to see what setting eliminates the noise.

The plan for us was to install an open energy ASHP kit and at the same time put in a bypass on the DHW circuit. But that depends on whether I’ll have time this summer.

And in answer to Marko, there’s no air in our system, so it’s not air.



PS Our ASHP is a cool energy unit and the tanks are both Newark ASHP tanks, so coils with a large surface area.

I had strange noises on my new heat pump install. They had plumbed the flow and return the wrong way around out the back of the heat pump. Noises went once corrected. A couple of weeks later, there was some alteration regarding the anti freeze valves and again, they mixed up flow and return so may we worth checking yourself…

I had lead installer on phone. There is no AAV but going to get authorisation to fully drain the system, fill it back up and put double dose inhibitor in. He don’t think it will make much difference and thinks it could be a tap a toilet washer or something like that causing it. Said it’s a days work to drain and fill everything.

It happens when heating has been on with hot water. Then you turn tap on flush toilet and you can hear it throughout house pipework. No idea of place but heard it vibrate the wall next door to where the tank pipes all are. But he’s been in and replaced them pipes. It happens different area of house different taps and toilets.

He’s just as stumped as me, which don’t help me.

Hopefully this eliminates the air theory.

Your water hammer is on the POTABLE (drinkable) side of the system not the primary side?

No idea

Just know the radiators are off at the moment so doubt they are causing it.

I also think the chart from the monitor is giving clues. But then I heard there is a faulty batch of these heat meters

Your symptoms appear to be a different issue.

@JustinUK’s primary system certainly appears to have air in it. You can see the electrical input continues and the supply/return temperatures continue to rise through the hot water cycle even as the flowrate drops to zero at 13:53ish in the excerpt provided. This is indicative of air in the primary that is dissolving out as the water warms up. There will be an info code / error code visible on the heat meter when this happens. He can confirm the presence of air in the primaries by checking this the next time this reoccurs.

The heat meter then appears to switch “integration mode” from integrating frequently to integrating less frequently (some models, to save battery, don’t integrate as frequently if there isn’t flow being measured, the theory being that if there is no flow being measured nothing much can be happening to the temperatures.

This makes little sense. Heat pumps cannot deliver space heating and hot water heating at the same time. Can you be more specific about when this occurs.

This I don’t understand. What do you mean by “power heating on” and “a few moments”

Did you push some “boost” button that changes the heat pump output / system flowrate?

You have given several different accounts of when the noise occurs.

Sometimes it’s when you push a button on the heat pump. Sometimes it’s when the heat pump is delivering heating and hto water (impossible). Sometimes it’s when you flush a toilet.

It is possible that there are bangs and clangs all over the place and different things are going wrong each time. It feels more likely that your descriptions are wanting to be more specific if the armchair guesses are to be more accurate.

All we CAN say from the armchair is that there’s air in your primary. (the heat meter chart shown evidences this)

You also have a contract with Octopus to install a heat pump to an “adequate” standard with “adequate” workmanship; so I’d be inclined to video the noise, post on youtube, then email octopus a link and ask them to rectify it as the first port of call. Doesn’t matter contractually if the lead installer on that job is stumped. They have an office with engineers to get their installers out of any pickle they create. :slight_smile:

Also to bleed the system properly. Such that the heat meter isn’t showing that there’s air in it.

Sorry read heating water as just the water

Radiators were not on at the time. It’s something to do with the heating of the hot water

I’ve no idea when these water hammer noises will happen or what the codes are on the heat meter. What I did was video the heat meter and cycled through the settings pressing both buttons but I have no idea what they all mean. I did video it on the phone, but file is massive and wont upload.

Assuming its air in the primaries as suggested, how best to get that air out? I’m told there is no AAV and I am attempting to get Octopus to drain the entire system.

To see error when it happens is next to impossible as heat meter is in the outside garage, and the tank is in the house upstairs, it lasts a few seconds.

When I say power heating I mean the heating power button (believe this is immersion rather than heat pump)

When you are heating the hot water, which takes tens of minutes, the flow rate in the heat meter is dropping to zero as the water heats up and the air dissolves out. This is not a “momentary” thing. In the example in your first post it lasts from 13:53 until the end of the heating cycle.

You can upload to YouTube and then share the link

I am not suggesting that this is the ONLY issue. It is ONE issue.

I would look at your contract with octopus and write to the address indicated.

I would say something like “Hi, we have a contract that you will do an adequate job of installing a heat pump, but unfortunately there is air in the primary system as evidenced by the heat meter. Please acknowledge this correspondence and let me know when you will be able to remedy the defect.”

Then leave it to them. If you’ve not had it fixed in a fortnight then ring amex/visa/MasterCard and issue a chargeback against octopus for failing to have delivered an adequate installation. Then write back to octopus to tell them that you’ve initiated the chargeback and will, unless they remedy the issues, by hiring an independent expert to investigate and resolve at octopus expense. (costs to be deducted from the chargeback and the balance of the chargeback returned to octopus if there is any left) That ought to resolve it by escalating to the appropriate people if the first set ignore your ask to finish the job off. At the very least there ought to be some means of purging air.

As to any other issues I can’t say. There isn’t enough information to guess from the armchair. A competent plumber with eyes on site will be able to offer more insight.

Attached youtube link - https://youtube.com/shorts/ZJoFLl-3Vgk?feature=share

There is someone fairly high up at Octopus looking into it. Just not got to the solution yet.

It’s suggesting the air is trapped and will always dissolves in the water and dissolves back out as the water heats up. It’s how they get that air out that I’m thinking if they drain the entire system and fill it up again, replacing R32 inhibitor (double dosed) that it may remove the air. Or is that not the way to go about it.

OK they are coming out on Monday to fix it. Octopus R&D are then going to be monitoring my system on heat pump monitor

Hopefully they can sort it all out for me.