Electrics and gas
A buffer cylinder is named and the cylinder-stat was not seen. What has the survey not confirmed about how the heat pump stores heat?
The survey has not confirmed how the heat pump stores heat. A buffer cylinder is named, so something calls a vessel a buffer, but the cylinder-stat was not seen. Without that stat the survey cannot confirm the control that should govern the store, or whether the buffer is wired as the name suggests. A glimpse of pipework is not a control. This visit did not test heat-pump efficiency and did not decide the store works. Storage remains a name plus a stat that was not found.
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?
Heat pumps often use a buffer so the system has volume and heat is on hand when the emitters need it. The thermostat on that vessel is part of how the store is called to heat. If the stat was not in view, it may be elsewhere, boxed in, or absent. The surveyor did not find it and did not guess a setting. The named buffer might be doing what the label implies, or it might not. Neither was confirmed. The gap is the unseen stat and the untraced control.
Ask the seller for a diagram and a commissioning sheet that show the buffer and the cylinder-stat. The survey has not verified those papers. Approved Document L is guidance for building work, not a verdict on this store, and the survey issues no building-regulations certificate. The Boiler Upgrade Scheme does not confirm a stat that was not on view, and grant eligibility is not decided here. If the control matters, an engineer can trace it. Tell a lender the buffer is named and the stat was not seen.
What should you ask your surveyor?
- Is the buffer identified by a label, by pipework, or only by the pack?
- Where was the cylinder-stat expected, and what was found in that place instead?
- Does an indoor controller claim a store reading the survey could not tie to a stat?
What are the typical next steps?
- Treat the way heat is stored as unconfirmed.
- Ask the seller for a diagram showing the buffer and the cylinder-stat.
- Do not tell a lender the store was tested when the stat was not seen.
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
Is a buffer the same thing as the domestic hot-water cylinder?
Not necessarily. A buffer often adds volume for the heating circuit, while hot water for the taps may be a different vessel or a combined one. The survey has not confirmed which arrangement this name means, and it did not see the cylinder-stat. Do not merge the two stores when you speak to a lender. Ask for the diagram.
If the house was warm, has storage been confirmed anyway?
No. Warm emitters on one visit do not show how a buffer is controlled or whether a stat exists. The cylinder-stat was not seen. The survey did not test efficiency or the store. Heat in a room can be produced in more than one way. How the heat pump stores heat stays unconfirmed until the control is found.