Electrics and gas
The hot water is an immersion heater and a header tank. What has the survey actually checked?
It has seen, if access allowed, a vented cylinder and a tank that feeds it. It has not tested the immersion, and it has not certified the tank. This is not the unvented-cylinder question. A header tank and an open vent are a different system, and the survey did not switch the heater on as a test.
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?
Vented cylinders are heated by an electric immersion, by a boiler coil, or by both. The surveyor looks at the cylinder, the tundish if there is one, leaks, and the cold tank in the loft if the hatch was safe to use. They do not electrical-test the immersion, and a standard inspection does not remove covers. A header tank with a lid askew, a corroded ball valve, or insulation falling off is a visual note. It is not a statement that the water is wholesome, and it is not an EICR. Landlords in the private and social rented sectors must have electrical installations inspected at least every five years. An owner-occupier seller is not under that duty.
Do not import rules for sealed, unvented cylinders into this cupboard. If the cylinder is unvented, the survey should say that instead. If it is vented, ask the seller which heat source they actually use. An immersion can be a backup that has not been switched on for years. Cold water at the tap does not, by itself, condemn it. If you want the circuit classified, that is an electrician. Any C1, C2, C3 or FI code is theirs, and it is not a RICS condition rating. The tank’s condition stays a plumbing note. Do not let one trade’s report pretend to cover both.
What should you ask your surveyor?
- Did you see a header tank, a vent, or a sealed unvented cylinder? Please name which.
- Did you test the immersion?
- Were there leaks, or only the equipment present?
What are the typical next steps?
- Do not switch the immersion on and leave it.
- Ask the seller whether the boiler, the immersion, or both heat the water.
- If you need the circuit tested, ask an electrician. Do not expect a gas engineer to certify the immersion.
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 rusty header tank an electrical fail?
No. It is a tank the survey could see. The immersion circuit was not tested.
Does a new cylinder prove the loft tank was renewed?
No. They are replaced on different days. The survey reports each one it saw.