Electrics and gas
A desuperheater is labelled on the cylinder and the hot taps were not run for long. Has domestic hot water been tested?
No. Domestic hot water has not been tested. A desuperheater labelled on the cylinder means a label says that device should help the heat pump warm stored water. The hot taps were not run for long, so the survey did not check how the store behaves, whether it recovers, or whether the labelled part actually heats it. No sample was taken. This visit did not test heat-pump efficiency. The report can note the label and the brief use of the taps. It has not tested domestic hot water.
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 desuperheater is meant to pass a little heat from the refrigeration circuit into stored water. That is not the same as proving the cylinder, a backup heater or the taps. A short run may only show that some warm water was already in the pipe. It does not show the store reheating or a control calling for heat. Labels can remain after the pipework has changed. The surveyor did not carry out a hot-water test and recorded no performance figure. A brief draw-off is a glance, not a test.
Ask the seller for the commissioning sheet that covers hot water and the desuperheater. The survey has not verified it. Approved Document L is guidance for building work, not a hot-water certificate from this visit. The Boiler Upgrade Scheme does not test the taps, and eligibility is not decided here. If the cylinder's behaviour must be known, an engineer can run a proper test of how the store is heated. Tell a lender the part is labelled and domestic hot water was not tested.
What should you ask your surveyor?
- Is the desuperheater identified only by a label, or by pipes that could be followed?
- Does the report limit what the short run of the taps actually showed?
- Is there a backup heater the survey also left untested?
What are the typical next steps?
- Treat domestic hot water as untested, whatever the cylinder label says.
- Ask the seller for the commissioning note that covers hot water.
- Do not quote a temperature or a recovery time this visit did not measure.
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 warm water at one tap clear the desuperheater?
No. One tap, used briefly, can be water that was already sitting in the pipe or the cylinder. It does not prove the desuperheater is heating the store. The survey did not run a hot-water test. A label plus a short draw-off is not that test. An engineer would watch the store heat, which this visit did not do.
Could the label remain after the part was removed?
Yes. The survey has not followed every pipe to prove the labelled desuperheater is still connected. Domestic hot water was not tested, so whether it works is unknown. Ask for the commissioning paper and, if needed, an engineer's inspection. Do not promote a label into a working component.