What is, and is not, acceptable when installing a heat pump.

[Egnaro]

Under MCS Guidance, if flexi pipes connect the HP to the internal pipework through the outside wall. Do the flexi pipes have to be insulated either by a wrap around product or expanding foam through both the outer and inner leaf?

 

I'm unable to find anything on the above looking through MCS literature.

[JohnMo]

Flexible pipes should be outside the wall not through it. All external pipes are to be insulated. Wall pipe should be sleeves and insulated.

[Egnaro]

Interesting.  This may be point number 1 from a long list of potential problems I'm going to find as I take a closer look.

 

As you can see from the photo (workmanship aside for now), there appears to be flexible pipes going through the inner leaf without insulation. When it passes through the outer brick it looks to have been treated with foam and cement.

 

 

 

 

[JohnMo]

Report MCS, that is rubbish. Looks like a monkey did it.

 

The grey cables are exposed to UV, so unless they are specifically designed for that, the insulation will fail.

[Egnaro]

Let me just say, that was one of the better points of the installation. The point of this thread is to establish if the plumbing and electrical work was done to a standard that would raise concerns with MCS and Napit.

 

I need to tread carefully until I can gather further information on the contractors, and investigate all the other electrical and pipework. So far, the overall installation is not looking good, the only positive is the HP appears to function.

 

I won't mention the solar at this stage, that is a whole other story of woe.

 

[JohnMo]

Hope you haven't handed over a bucket load of cash

[marshian]

26 minutes ago, Egnaro said:

Interesting.  This may be point number 1 from a long list of potential problems I'm going to find as I take a closer look.

 

As you can see from the photo (workmanship aside for now), there appears to be flexible pipes going through the inner leaf without insulation. When it passes through the outer brick it looks to have been treated with foam and cement.

 

 

 

 

 

I would not be happy with that if I'd done it myself!!!

 

I'd be really Expletive unhappy if I'd paid for it to be done like that!!!

[Egnaro]

No money exchanged hands, thank god !

[Dillsue]

1 hour ago, Egnaro said:

No money exchanged hands, thank god !

Great and keep it that way until you've done a full QA check. I have an inkling that if you complain to MCS they'll send someone out to have a look

[Egnaro]

I've been asked to cite the specific part of 'any' guidance that says you either 'cannot', or 'it is not best practice' to run flexible pipework through an outside wall. Or to omit suitable sleeving / insulation when flexible pipework is sited through an outside wall.

 

Can anyone point me to the relevant part in any guidance literature? I cannot find it in any of the MCS, Planning, Building Regs, or other documents. 

 

As much as I would love to discuss at least another ten examples that are far worse than in the photo above, at this stage I need to be cautious until I can establish if what the installers have done goes against specific guidance by any regulatory body.

[Marvin]

The flexible pipes form the ASHP unit are designed to absorb any vibration from the ASHP unit and should connect to rigid pipes before entering the building as far as I understand and is what I have done.

 

Bare electrical cable outside? no no no. (not even cables used for controls)

 

A lot of this will be covered under electrical regulations, plumbing regulations, building regulations and manufacturers specifications. We had to have an electrical isolator and plumbing isolator valves outside so the unit can be isolated by anyone doing maintenance.

 

Check the size of the primary flow and return pipes with the ASHP manufacturer's requirements (ours had to be 28mm to port valves and back to ASHP)

 

Another one that was not oblivious was the sizing of the power cable to the ASHP unit. We were advised that ASHP's are effected by a small voltage drop and we increased the size of the cable to reduce voltage drop along the cable. (not due to the power demand).

 

Anyway I'm sure I will be corrected on this if need be....

 

 

Good luck

 

Phil.

 

 

 

 

Edited February 12 by Marvin

[SteamyTea]

1 hour ago, Egnaro said:

I've been asked to cite the specific part of 'any' guidance that says you either 'cannot', or 'it is not best practice' to run flexible pipework through an outside wall. Or to omit suitable sleeving / insulation when flexible pipework is sited through an outside wall.

Is it hidden in here:

https://www.waterregsuk.co.uk/guidance/requirements-guidanc/

 

(try searching for heating within the document, Ctl+F)

[mk1_man]

Personally I don't see any issue with running flexi's through the cavity wall. Some installs don't offer you the space to have them outside i.e. on out heat pump it is a straight 300mm run and then into the cavity. The picture above suggests same lack of space issue here also.  I would however have thought any pipe be it flexi or rigid would certainly need to be correctly insulated when going through the cavity.  We used a straight run of Primary Pro straight through.  To be honest with our setup we don't even use the flexi's as I was unhappy with the bore reduction.  Absolutely no noise / vibration issues either.

 

[Dillsue]

AKAIK flexys fail way sooner than ridgid pipe so you want them out in the open where you can see them starting to drip. If they split in the cavity they could be there leaking for a long time soaking the building fabric rather than dripping onto the outside floor.

[joth]

8 hours ago, Egnaro said:

I've been asked to cite the specific part of 'any' guidance that says you either 'cannot', or 'it is not best practice' to run flexible pipework through an outside wall. Or to omit suitable sleeving / insulation when flexible pipework is sited through an outside wall.

 

Can anyone point me to the relevant part in any guidance literature? I cannot find it in any of the MCS, Planning, Building Regs, or other documents. 

 

As much as I would love to discuss at least another ten examples that are far worse than in the photo above, at this stage I need to be cautious until I can establish if what the installers have done goes against specific guidance by any regulatory body.

It needs to be serviceable.

On a practical note, how do you make it airtight and yet serviceable?

I had a flexipipe fail, I'd have been even more pissed off if I'd ruined my house airtightness in the process of replacing the pipe. 

[Egnaro]

You will be surprised to hear they are no regulations preventing flexi pipes being placed through an outside wall, with or without, insulation.

 

Unless someone knows the exact, or a conflicting regulation from an unknown kwango. Water Regs, Building Regs, and the MCS allow this method.

 

 

[Nick Laslett]

31 minutes ago, Egnaro said:

You will be surprised to hear they are no regulations preventing flexi pipes being placed through an outside wall, with or without, insulation.

 

Unless someone knows the exact, or a conflicting regulation from an unknown kwango. Water Regs, Building Regs, and the MCS allow this method.

 

 

Thank you for following through with this information. 
 

I wonder if somewhere in the details of one of the plumping standards CIBSE and CIPHE, there is something about flexi pipes being easy to access for maintenance. The ASHP guide I have from MCS defers to CIBSE & CIPHE for pipework. 
 

This is what Google AI threw up. 
 

Quote

 

The Chartered Institute of Plumbing & Heating Engineering (CIPHE) has warned that some flexible hoses used for washbasin taps can be unsuitable for plumbing systems. This is because the inner surfaces of the hoses can be a place for bacteria to grow. 

Explanation

Flexible hoses, also known as flexi pipes, are used to connect parts that can move. They can be made from rubber or plastic. 

They are designed to handle stress from vibration, thermal expansion, and other forces. 

They are often found under sinks in kitchens, bathrooms, and laundry rooms. 

Flexible hoses are more likely to fail than properly fitted metal pipes. 

Corrosion can cause flexible pipes to burst, especially in areas with hard water. 

Flexible hoses can kink or split if they are not fitted correctly. 

Flexible hoses can leak if they are pulled too tight. 

Legionella bacteria can be found in flexible pipe hose tap connectors. 

To ensure that flexible hoses are not kinked or damaged, it is important to measure and cut the pipe work correctly. 

 

You could also try the flexi pipe manufacturer for their install requirements. 
 

https://www.bes.co.uk/flexible-hose-1-bsp-f-swivel-elbow-x-28mm-x-300mm-pair-25286/

 

The Primary Pro who make ASHP pipe insulation are very specific about the wall cavity.

 

https://primarypro.co.uk/products-and-tools/#section-241-136

This post on Screwfix forum, which you might have seen says “The flexible pipe should never cross the cavity. ”

 

https://community.screwfix.com/threads/how-to-seal-around-a-pipe-breaking-a-cavity-wall.12052/

Anyway, I’m intrigued enough to search a little more. 

 

[Egnaro]

@Nick Laslett

 

That is useful information. 

 

It does highlight how many of us automatically link 'poor quality of work' to a regulation. 

 

 

[Nick Laslett]

@Egnaro, I have spent a little time researching this. 
 

I am pretty confident that BR, NHBC, Water Regs, CIPHE all say that a pipe passing through a wall must be sleeved. 
 

I found this reference in the Plumbing level 2 NVQ course book I have. 
 

“All pipes that pass through wall structures must be sleeved.”

 

Here is an attached image from WRAS

I don’t know if that helps. 

 

[Egnaro]

@Nick Laslett

 

That is useful and a good starting point.

 

I've received a few responses from the flexi pipe manufacturers and UK suppliers. All have different takes on the subject ranging from 'not a good idea' to ' that's not the purpose of the flexi pipe'. None can cite a regulation.

 

Building control say that 'pipes are to be suitably sealed when they pass through a building', but they place the onus on competent people who in general certify their own work. I think that last comment may hint that self certification may not meet BC regs ?

[sharpener]

On 20/02/2025 at 10:49, Egnaro said:

I think that last comment may hint that self certification may not meet BC regs ?

 

Certainly you can self-certify electrical work, by co-incidence this morning I received the final cert for installing my own battery system, new CU in garage and EVCP. But they require a Building Notice and then inspect, and also want you to complete the usual elec installation paperwork.

 

Re DIY plumbing IME they just visit and inspect unless it is something highly specific like G3 work.

 

In the case of flexis I personally would not want any part of them to be inaccessible. The whole point of them being able to flex is rather negated if they are encastered in the building fabric.

 

 

Edited February 21 by sharpener

[Egnaro]

@sharpener

 

Indeed. If I put the installers hat on, I could argue that the pipework from the HP to the point it enters the wall is still a flexi, so only a small part is encased and the rest is allowed to flex and absorb vibration.

 

BC say if it meets the MCS criteria (which it does) and the manufacturers spec, then it meets their requirements - despite the comment from BC noting it was an utter bodge. It is only when you close read the MSC guidance that you find it is found wanting.

[Bramco]

2 hours ago, Egnaro said:

BC say if it meets the MCS criteria (which it does)

 

We had a random MCS inspection on our ASHP install - he picked up the fact that the pipes through the wall weren't sleeved - these weren't the flexis.  With the constraints we had, we didn't want the bozos doing the install hacking at our lovely corrugated metal cladding, so we'd not let them put in any sleeving. They could just get through, under the bottom edge of the cladding.

We had to provide the wall makeup as well as confirmation that we were happy with having no sleeving, so that the MCS guy was happy.

So they, or at least he, thought sleeving should have been installed.

[Big Jimbo]

It's about a million years ago that I was Corgi registered for gas. We always used to sleeve pipes through walls. 15mm through 22mm. 

22mm through 28mm etc. Are you really allowed to put pipes through walls with no protection these days ?

[Egnaro]

@Bramco @Big Jimbo

 

WRS regs can be misinterpreted, but ultimately they do say any pipework through a wall has to be sleeved as noted above by @Nick Laslett

 

However, much of this is now a moot point as the installation criteria laid out by the Heat Pump manufacturer specifies pipes do indeed have to be sleeved and insulated when going through walls

 

At least that is good news...for me anyway !

 

As for the MCS, well what can I say! I recently spent a lot of time reading through their self promoting high standards material. I've concluded that almost any DIY person who can hold an hammer in one hand, and a lit ciggie in the other could install a heat pump to MCS Guidelines whilst reading a copy of the Beano.  I was amazed that BC accept they have to leave standards in the hands of these kwangos as it's become so complicated and time consuming to enforce 'any' standard these days.   There is a wide gap between bodging and satisfying regulations. If my example above is within any guidance then no wonder new builds from the large corporates are in such a state.

 

I'm now on a long road seeking redress that I expect will take at least a year and involve various regulatory bodies. As I've already said, this is just one element from a catalogue of errors. Perhaps one day I can tell the full story. From your responses so far, I imagine jaws will hit the ground.

 

Where I can, I will update this thread along the way.