Electrics and gas
The pack mentions glycol in a slinky trench for a ground-source array. Did the home survey excavate or test that brine circuit?
No. The home survey did not excavate the slinky trench and did not test the brine circuit. The pack mentions glycol in a ground-source array, which is a description of fluid in buried pipes. That fluid is not verified by reading a sentence. The trench was not opened, the liquid was not sampled and the pressure was not tested. This visit did not measure heat-pump efficiency. The report can note what the pack claims. It has not confirmed the array, the fluid or that the circuit is intact.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
A slinky is a coiled ground loop in a trench, so the heat pump can take heat from the ground. The pipes are buried. A walk on the lawn shows turf, not the coil and not the glycol. Leaks, trapped air or a weak mix would show only with an installer's tests. The survey does not carry those out. Approved Document L is guidance for building work, not a test sheet for a brine circuit, and this survey does not issue a building-regulations certificate. The pack's mention stays a mention.
Ask the solicitor for the array layout, the commissioning record and any note of the glycol fill. Those papers were not turned into test results by this visit. The Boiler Upgrade Scheme, in England and Wales, does not prove a trench on a resale inspection, and the survey does not decide grant eligibility. If the circuit must be proved, a ground-source engineer can test it. Tell a lender the array is described in the pack and was neither dug up nor tested.
What should you ask your surveyor?
- Is the slinky only in the pack, or was a manifold in the house also seen?
- Does the report record glycol in a vessel, or only as a written claim?
- Is there a layout that shows the trench the survey did not open?
What are the typical next steps?
- Treat the glycol and the slinky as claims in the pack, not as test results.
- Ask the seller for the array layout and the commissioning record.
- Do not tell a lender the brine circuit was excavated or tested.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Does a warm house prove the ground array is working?
No. Heat in the rooms can come from the heat pump, from a backup heater or from a mild day. The survey did not test efficiency and did not open the trench. Comfort is not a brine test. The circuit stays unverified until an engineer tests it, or until commissioning papers are at least read for what they claim rather than as proved fact.
Could the trench have been filled without glycol?
Yes. The pack says glycol. The survey did not sample the fluid, so it cannot confirm the mix or rule out something else in the loop. Do not repeat the pack's word as a finding made on site. The fluid was described and not tested. That is all this visit knows about it.