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Surface mount or bury primaries for heat pump installation?

tomasmcguinness · 2025-06-21T16:58:07Z

Hi, I'm in the early stages of planning my heat pump installation and whilst I know where the pump itself will be sited, I need to work out how to get the water into the garage. The path will see the pipes run up the side access and turn into the garage before getting connected to my heating. The route includes data and power cable. I have two options. 1. I surface mount the primaries and run them along my neighbour's wall. I then have to either go under the paving or run the pipes up an over. I'll need a bracket of some sort between my neighbour's wall and the heat pump itself as I can't fix them to their failing timber fence. 2. I bury an instulated pipe that holds everything. The problem is that my side access is pretty busy underground with storm, waster and water main pipes. I'm told I should bury the pipe at 600mm, but I don't believe that's possible. At least not all the way. I have photos of this before it was backfilled. What I want to know is why we can surface mount pipes in insulation, but we're required to put insulated pipes quite deep in the ground. Has anyone got their primaries buried at a depth less than 600?

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Air Source Heat Pumps (ASHPs)

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tomasmcguinness

(@tomasmcguinness)

Trusted Member Member

Joined: 2 years ago

Posts: 27

Topic starter 29/06/2025 9:52 am

What about those pipes that include conduits for electrical cables such as Isoflow or Uponor?

Owner of a ridiculously oversized 35kW boiler and trying to make it as efficient as possible. 4.8kW solar PV with 5.4kWh storage. EV driver.
Follow my journey at https://www.youtube.com/@tomasmcguinness
Heat pump installation has started!

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Transparent

(@transparent)

Famed Member Moderator

Joined: 4 years ago

Posts: 3198

29/06/2025 3:17 pm

Can we have some links to those you're considering please @tomasmcguinness ?!

I think we're basically going to say "follow the manufacturer's instructions",
but it would still be good to check out what those are.

Save energy... recycle electrons!

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Aventus Eco

(@aventus-eco)

Active Member Member Professional Installer

Joined: 1 year ago

Posts: 7

01/07/2025 10:17 pm

@tomasmcguinness, I think your best bet would be using underground ducting. You can get pre-insulated pipe for the flow and return, plus an additional two ducts, one for the power cable and one for the data cable.

At the ends, when everything comes up out of the ground, you can use press fittings to connect onto copper or, even better, insulated MLC pipe. If you go with copper, just make sure you insulate it properly with something like Primary Pro.

There are a few different manufacturers out there, but City Plumbing stock the ducts… you just tell them the length you need, and they’ll cut it to size and can do next-day delivery.

Also, make sure you get the proper end seals where the duct exits the ground. You basically heat it up with a heat gun and it seals the duct tight around any pipes, just like electrical heat shrink. It’s dead easy.

As for depth, 600mm is standard guidance to protect from frost and spade damage, but if you're struggling with that, going a bit shallower isn’t usually a big issue. Frost isn’t a real concern here since your flow and return will be in an insulated duct, unlike a mains water pipe. attached are some links and install guidance PDF.

Pre-Insulated Underground Pipes

INS140-3225-2HSC - Pre Insulated Pipe 140mm x 25mm or 32mm Heat Shrink Cap | Polypipe

pre-insulated_installation_guide_0.pdf

This post was modified 11 months ago by Mars

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