Electrics and gas
A low-loss header sits between the heat pump and the radiators and no label was read. What mixing of the two circuits was left untested?
The mixing of the two circuits was left untested. A low-loss header sits between the heat pump and the radiators so those circuits can run at different flows, and no label on it was read. Without that label the survey has not recorded the maker or the settings. It did not measure flow on either side and did not check whether the circuits stayed separated as designed. The header was seen. How the two sides mix, or whether they mix too much, stays unknown. Efficiency was not tested, and no building-regulations certificate was issued.
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 low-loss header is a meeting point. The heat pump can circulate on one side while the radiators circulate on the other, which is meant to stop one circuit starving the other. If the header is piped or set wrongly, the two flows blend and the radiators never see the design the installer intended. A label would at least name the unit. An unread label plus no measurement leaves even that start unmade. The survey describes a box and some pipes. It does not commission them.
Ask the solicitor for any commissioning sheet or design drawing, and keep it off the survey text. Approved Document L is energy-performance guidance for building work. It is not a reading taken from this header. A heating engineer can test the two sides if you need that. Tell a lender the header was unidentified and untested. Do not describe the heating as balanced because both sets of pipes were present. Presence is not a mixing test.
What should you ask your surveyor?
- Was the header's label read?
- Was mixing between the pump circuit and the radiators measured?
- Has efficiency of the heat pump been tested?
What are the typical next steps?
- Treat the mixing of the two circuits as untested.
- Ask the solicitor for any commissioning sheet.
- Do not describe pipework as a balanced system.
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 radiator prove the header is working as designed?
No. A warm radiator, if one was felt, shows some heat arrived. It does not show the two circuits are separated, or that flows match a design. The label was not read and no measurement was taken. Ask for the commissioning paper. Do not promote warmth into a test of the header.
Is Approved Document L a certificate for this installation?
No. Approved Document L is energy-performance guidance for building work. The survey does not issue a building-regulations certificate, and it did not apply that guidance as a pass for this header. The unread label and the untested mixing remain the finding. Papers for the installation, if they exist, belong with the solicitor.