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How to Survey a Cylinder Cupboard for a Heat Pump
A practical guide to measuring and recording the complete cylinder installation space.
- Last updated: September 2026
- Heat Loss Hub · For Installers
A heat-pump cylinder survey should record much more than the width and depth of an airing cupboard. The designer may need to understand the available installation space, the size of the cupboard opening, how a new cylinder could reach the cupboard, what cylinder is currently installed, existing heating pipework, domestic hot and cold-water connections, safety-discharge routes, space for valves, controls and an expansion vessel, electrical and immersion-heater access, floor construction, future service access, household storage constraints, and any information that remains uncertain.
The aim is to create an accurate record of the location before the required cylinder is selected.
The cylinder is only one component of the cylinder installation.
KEY TAKEAWAY
The survey records the installation space. The design determines what cylinder belongs in it.
GET IN TOUCH
Send us the completed cylinder-location survey and we’ll select and size the cylinder against the actual space.
What Information Should Be Recorded?
| Information | Why It Matters |
|---|---|
| Location reference | Keeps possible cylinder locations traceable |
| Internal dimensions | Shows the physical installation space available |
| Door dimensions | Shows whether a cylinder can physically enter |
| Delivery route | Establishes whether the cylinder can reach the location |
| Existing cylinder | Supports later retain-or-replace assessment |
| Primary connections | Shows how the heating system reaches the cylinder |
| Domestic-water connections | Records the existing hot and cold-water services |
| Safety discharge | Shows whether a suitable discharge route can be designed |
| Ancillary-component space | Allows for vessels, valves, controls and pipework |
| Service clearance | Allows future maintenance and component replacement |
| Electrical provision | Records the starting point for immersion and controls |
| Floor/support | Identifies possible structural considerations |
| Storage constraints | Records the impact on the household |
| Photos/video | Provides supporting evidence |
| Confidence | Separates confirmed information from assumptions |
A cylinder-cupboard survey should describe the complete installation space, not just the empty dimensions.
Use Candidate Cylinder Locations
The existing airing cupboard does not automatically have to be the final cylinder location. Where a property has more than one realistic option, record each one separately.
For example: CYL-LOC-01 — Existing airing cupboard, CYL-LOC-02 — Utility room, CYL-LOC-03 — Garage.
Each location can then be assessed during design for available space, delivery route, primary pipe route, domestic-water connections, safety-discharge route, service access, floor/support, electrical access, installation disruption and loss of household storage.
One location may have better pipework connections while another offers considerably more space and easier servicing.
KEY TAKEAWAY
Survey the existing cupboard, but do not assume it is automatically the best cylinder location.
Measure the Cupboard
Start with the physical space. Record internal width, internal depth, floor-to-ceiling height, usable height, door opening width, door opening height, shelves, pipe boxing, wall projections, sloping ceilings, existing services and fixed obstructions.
Measure the usable dimensions rather than the apparent size of the cupboard. A pipe box, shelf or structural projection can significantly reduce the space available for the installation.
Do not rely on one generic minimum cupboard size. Cylinder dimensions, connections and service requirements vary between products.
KEY TAKEAWAY
Measure the available space first. Apply the selected cylinder’s dimensions and service requirements during design.
Measure the Route Into the Cupboard
A cylinder that fits inside the cupboard is no use if it cannot physically reach it. Survey the route from the property entrance to the proposed cylinder position.
Depending on the property, record external entrance, door widths, hallway width, stair width, landings, tight turns, handrails, low ceilings, changes in level, loft hatch dimensions where relevant, and final cupboard opening.
Pay particular attention to the narrowest or most difficult part of the route. A tall cylinder may also need space to turn, tilt and eventually stand upright.
Think about removal as well as installation. The existing cylinder may have to come out, and the new cylinder may eventually need replacing.
KEY TAKEAWAY
A cylinder that fits in the cupboard still has to get into the cupboard. Measure the route into the cupboard as well as the space inside it.
Record the Existing Cylinder
Where a cylinder is already installed, record as much reliable information as possible. Useful information includes manufacturer, model, capacity, vented or unvented, direct or indirect, number of coils, product label, immersion heaters, visible connections, expansion vessel, safety controls, approximate age where known, and general condition.
Photograph the product label clearly enough for the information to be read later.
Do not assume that an existing cylinder can be retained simply because its storage capacity appears suitable. Heat-pump compatibility also depends on factors such as heat-exchanger performance and the requirements of the selected system.
KEY TAKEAWAY
Record the existing cylinder accurately. Do not assume that capacity alone determines whether it can be retained. The survey records what is installed. The design determines whether it is suitable.
Survey the Complete Installation Space
The cylinder body is only part of the installation. Depending on the system, space may also be required for expansion vessel, cold-water controls, safety valves, tundish, primary flow and return, domestic hot and cold-water pipework, isolation valves, sensors, wiring and controls, immersion heater, drain point and service access.
A cupboard may therefore be large enough for the cylinder itself but too restricted for the complete installation.
KEY TAKEAWAY
The cylinder is only one component of the cylinder installation. A cylinder can fit while the complete installation still does not.
Record Service Clearance
The equipment will need to be maintained after installation. Record the available access to areas that may contain immersion heater, thermostats, temperature sensors, safety valves, cold-water controls, expansion vessel, coil connections, drain point and electrical connections.
Do not consider only whether a component can be reached. Some components need physical space to be removed. An immersion heater, for example, may require withdrawal space beyond the side of the cylinder.
The selected product’s actual service requirements should be checked during design.
KEY TAKEAWAY
The cupboard must fit the service space as well as the cylinder. Service clearance includes the space needed to remove components, not just reach them. A cylinder that can be installed but cannot be maintained has not been properly surveyed.
Survey the Walls and Voids
The available floor area tells only part of the story. Record left wall, right wall, rear wall, ceiling, floor, existing pipe penetrations, existing service voids, pipe boxing, route into the floor below, route into the ceiling or loft above, and possible wall space for ancillary components.
This can help establish where pipework, vessels, valves and controls could potentially be accommodated.
Survey the walls and voids around the cylinder, not just the floor area underneath it. Photos of the complete cupboard are particularly useful here.
Record how the existing heating system reaches the cylinder location. Where visible, record primary flow, primary return, pipe sizes, pipe material, entry point into the cupboard, route toward the heat source, changes in level, visible restrictions and hidden sections.
Do not assume that the pipes connected to the existing cylinder will automatically be suitable for the new system.
KEY TAKEAWAY
The survey records the route and existing services. Hydraulic design determines what the new system actually requires. The cupboard may have enough space for the cylinder but not enough space for the pipework needed to make it work.
For a wider assessment of the heating distribution system:
Record the Domestic-Water Connections
The survey should also record the domestic-water services around the cylinder. Where present, identify incoming cold-water supply, hot-water outlet, balanced cold-water connection, secondary return, existing valve set, existing cylinder connections, visible pipe sizes and accessibility.
Record what can actually be seen. Do not guess the route of concealed services simply because their likely destination appears obvious.
The final domestic-water arrangement should be determined as part of the cylinder and installation design.
Survey the Safety-Discharge Route
Where an unvented cylinder is proposed, the safety-discharge arrangement is an important part of the installation. Do not survey the cupboard without considering whether a suitable discharge route appears possible.
Record existing tundish where present, existing discharge pipe, possible tundish position, route away from the cylinder, changes in level, available fall, wall or floor penetrations, route toward the outside or other termination, obstructions and existing termination where present.
If an existing discharge pipe disappears behind boxing or beneath a floor, record the point at which its route becomes unknown. Do not assume that an existing route is compliant simply because it is already there.
KEY TAKEAWAY
Do not survey the cylinder cupboard without surveying where a safety discharge can go. The survey establishes the available evidence and possible route. The final discharge arrangement should be designed and installed by the appropriate competent person in accordance with the applicable requirements.
Record Expansion-Vessel and Control Space
Do not allocate every available millimetre to the cylinder itself. The installation may also need room for equipment such as expansion vessel, vessel bracket, inlet control group, safety valves, isolation valves, sensors, wiring centre or controls, and associated pipework.
Record usable wall space as well as floor space. Also consider whether these components would remain accessible once the cylinder is installed.
Space around the cylinder is part of the installation, not unused space waiting to be filled.
Record Electrical and Immersion-Heater Access
Record the electrical starting point around the cylinder location. Useful information may include existing immersion heater, number of immersion heaters, existing electrical supply, local isolation, cable route, control wiring, available working space, and immersion-heater withdrawal space.
Do not remove electrical covers or expose live components as part of a general survey. Where further electrical investigation is required, flag it for the appropriate competent person.
KEY TAKEAWAY
The survey should record not only whether the immersion can be reached, but whether it can be removed.
The detailed electrical survey is covered separately:
Survey the Floor and Support
A cylinder becomes significantly heavier when filled with water. Record what is known about the surface supporting the proposed installation. This may include ground floor, first floor, loft, concrete floor, suspended timber floor, unknown floor construction, existing cylinder position, visible floor condition, visible reinforcement, joist direction where known, signs of movement or damage, and any structural concerns.
Do not use a visual survey to provide structural approval where the construction or capacity is uncertain.
KEY TAKEAWAY
The survey records what supports the cylinder. Structural adequacy should be verified where there is doubt.
Record Unusual Environmental Conditions
Most cylinder locations are inside the heated part of the property, but this is not always the case. Record if the proposed location is within an unheated garage, loft, external store, very cold space, damp area, flood-prone area, or particularly difficult-access area.
Also record any other environmental condition that may influence product selection, insulation, frost protection or servicing.
KEY TAKEAWAY
Record unusual environmental conditions early so they can be considered during product selection and installation design.
Record Household Storage Constraints
An airing cupboard is often more than a plant space. It may currently contain shelving, towels, bedding, clothes, cleaning equipment and general household storage.
Record shelves or storage that may need to be removed or altered. Where the impact could be significant, record the customer’s requirements as part of the survey.
A technically possible installation is not necessarily an acceptable solution for the household.
KEY TAKEAWAY
A cupboard can be technically usable while still creating an unacceptable loss of household storage. The design should work for the property and the people living in it.
Photos and Video
Photographs should allow somebody who has never visited the property to understand the cylinder location. Useful photographs include cupboard with the door fully open, complete existing cylinder, cylinder label, left side, right side, rear where visible, space above the cylinder, floor, primary pipe connections, domestic-water connections, safety valves, tundish, discharge pipe, expansion vessel, immersion heater, electrical connections, door opening, and wider access route where restricted.
Where the cupboard is particularly congested, a slow video from the doorway around the installation can provide useful context.
A close-up of the cylinder does not show whether the cupboard works as an installation space.
For general survey photography guidance:
Use Measurements, Not Assumptions
Record actual dimensions wherever reasonably possible. Important measurements can include internal width, internal depth, available height, door width, door height, narrowest access point, service space, available wall space and approximate pipe routes where relevant.
Do not rely on statements such as “It’s a normal airing cupboard,” “There should be enough room,” or “The new cylinder should fit where the old one is.”
“It should fit” is not a survey measurement.
Where something cannot be measured or confirmed, record the uncertainty.
Confirmed, Inferred or Unknown
Not every part of an existing installation will be visible. It is useful to classify important survey information as:
Confirmed
Measured or clearly observed.
Inferred
Strongly indicated by the available evidence but not completely verified.
Unknown
Cannot be established from the survey evidence.
For example: Cold-water supply route — confirmed. Discharge pipe behind boxing — inferred. Floor construction beneath finish — unknown.
KEY TAKEAWAY
Hidden services should remain uncertain until the survey provides evidence. An unknown route should not quietly become a confirmed design input because somebody needs to enter an answer into a form.
Example Cylinder-Location Record
A completed record might look like this:
| Field | Example |
|---|---|
| Reference | CYL-LOC-01 |
| Location | First-floor airing cupboard |
| Internal width | 780mm |
| Internal depth | 820mm |
| Available height | 2140mm |
| Door width | 620mm |
| Door height | 1980mm |
| Existing cylinder | 150L indirect |
| Cylinder label | Recorded |
| Floor | Suspended timber |
| Primary route | Floor void |
| Cold supply | Present |
| Hot outlet | Present |
| Discharge route | Existing route identified |
| Expansion-vessel space | Limited |
| Immersion access | Front |
| Service access | Review required |
| Delivery route | Tight stair turn |
| Storage impact | Two shelves would be removed |
| Photos | Complete |
| Confidence | Confirmed |
The location can then be recorded as: Candidate cylinder location — technical assessment required
rather than: Cylinder location approved.
A survey should finish with evidence, not premature approval.
Comparing Candidate Cylinder Locations
Where more than one location is available, record each one separately. For example:
| Factor | CYL-LOC-01 | CYL-LOC-02 |
|---|---|---|
| Space | Limited | Good |
| Delivery route | Tight | Good |
| Primary pipe route | Short | Longer |
| Discharge route | Existing | New route required |
| Service access | Limited | Good |
| Floor/support | Review required | Good |
| Storage impact | High | Low |
| Installation disruption | Low | Medium |
The survey does not need to select the final location. Its job is to create comparable evidence for the design.
KEY TAKEAWAY
The survey collects comparable evidence. The design chooses the location.
When Further Investigation Is Required
Some cylinder locations cannot be confirmed from the first survey. Further investigation may be needed where internal dimensions are incomplete, delivery route is uncertain, existing cylinder cannot be identified, existing pipework disappears into inaccessible areas, safety-discharge route is unknown, floor construction is uncertain, structural support requires verification, service clearance appears inadequate, there is insufficient space for ancillary components, electrical provision is uncertain, or access depends on building alterations.
Possible survey statuses include: Ready for cylinder selection, Additional survey information required, Discharge-route review required, Structural review required, Electrical review required, Alternative location should be considered.
This keeps uncertainty visible rather than forcing an early yes-or-no decision.
Common Cylinder-Cupboard Survey Mistakes
Measuring Only the Cupboard Floor
Problem: The complete installation may also need wall space, overhead space and service access.
Better: Survey the entire installation space.
Ignoring the Cupboard Doorway
Problem: A large cupboard can still have a narrow entrance.
Better: Measure the clear door opening.
Ignoring the Route Through the Property
Problem: Stairs, landings and tight turns can prevent a cylinder from reaching an otherwise suitable location.
Better: Check the complete delivery route.
Assuming the Existing Cylinder Can Be Replaced Like-for-Like
Problem: The new system may require a different cylinder arrangement.
Better: Record the existing cylinder and allow the design to determine what is required.
Assuming Capacity Determines Compatibility
Problem: Cylinder volume is only one part of selection.
Better: Record the product information and leave heat-exchanger suitability and recovery to the cylinder design.
Forgetting the Expansion Vessel and Controls
Problem: The cylinder body is only part of the installation.
Better: Record usable space around the cylinder as well.
Ignoring Service Access
Problem: Equipment will need maintenance after installation.
Better: Check whether important components can be reached and removed.
Forgetting Immersion-Heater Withdrawal Space
Problem: Being able to see or touch the immersion heater does not mean it can be replaced.
Better: Record the physical space available in front of it.
Not Tracing the Safety-Discharge Route
Problem: An unvented cylinder still needs an appropriate safety-discharge arrangement.
Better: Record the existing or potential route and clearly identify any hidden sections.
Assuming an Existing Discharge Route Is Suitable
Problem: Existing does not automatically mean correct.
Better: Record what is there and leave final compliance assessment to the competent person.
Ignoring Floor Construction
Problem: The cylinder will impose a substantial load when full.
Better: Record the supporting structure and flag uncertainty.
Looking Only at Existing Pipe Connections
Problem: A new cylinder may require a different pipe arrangement.
Better: Record the available routes and surrounding space.
Ignoring Household Storage
Problem: Removing shelves from an airing cupboard can have a real impact on the customer.
Better: Record the constraint before the design is finalised.
Approving the Location During the Survey
Problem: Physical fit is only one part of cylinder selection.
Better: Collect the evidence first and complete the technical assessment afterwards.
A cylinder cupboard should be surveyed as an installation space, not as an empty box.
Cylinder-Location Completeness Check
Before completing the survey, confirm: candidate location referenced, internal width measured, internal depth measured, available height measured, door width measured, door height measured, delivery route checked, existing cylinder recorded, cylinder label photographed, primary connections recorded, domestic-water connections recorded, safety-discharge route recorded, expansion-vessel space recorded, control space recorded, immersion/electrical access recorded, service clearance recorded, floor/support recorded, storage constraints recorded, photos complete, video taken where useful, confidence recorded, and critical unknowns flagged.
The survey can then be marked: Ready for cylinder selection, or Further information required.
What Happens After the Cylinder-Location Survey?
The cylinder survey provides the physical information needed for the hot-water design. The process may then look like this:
Candidate cylinder location surveyed → Hot-water demand assessed → Required storage volume established → Heat-exchanger and heat-pump compatibility assessed → Cylinder selected → Selected cylinder dimensions checked against surveyed space → Service requirements checked → Safety-discharge arrangement designed → Primary and domestic-water routes confirmed → Electrical requirements confirmed → Floor/support verified where required → Location approved or alternative selected
The cylinder should not be chosen independently of the property, and the cupboard should not be approved independently of the cylinder.
KEY TAKEAWAY
The survey establishes what space is available. The design determines whether the required cylinder can be installed there.
Frequently Asked Questions
Measure the complete installation space rather than only the existing cylinder. Record internal width, depth and height, door dimensions, delivery route, existing cylinder, primary pipework, domestic-water connections, safety-discharge route, space for ancillary components, service access, electrical provision, floor/support, photos and any uncertainty.
There is no single cupboard dimension suitable for every heat-pump cylinder. Cylinder dimensions and service requirements vary between products. Measure the available space accurately and compare it with the selected cylinder and the space required for its connections, controls and servicing.
Possibly. The cupboard needs to accommodate more than the cylinder body. The assessment should consider cylinder dimensions, door opening, delivery route, pipework, valves and controls, expansion equipment, safety discharge, immersion access and service clearance. A detailed survey allows the required cylinder to be checked against the actual space.
That depends on the dimensions of the selected cylinder and how it needs to be moved into position. Measure the clear opening rather than the nominal door size. Also check stairs, hallways and turns leading to the cupboard.
Sometimes, but cylinder capacity alone does not determine suitability. The design should consider hot-water demand, cylinder capacity, heat-exchanger performance, heat-pump compatibility, recovery, condition and controls. The survey should record the existing cylinder accurately so that assessment can take place.
Where possible, record manufacturer, model, capacity, product label, direct or indirect, vented or unvented, number of coils, immersion heaters, visible connections, expansion vessel and safety controls. A clear photograph of the cylinder label can be particularly useful.
That depends on the cylinder and system arrangement. The survey should not assume a particular configuration. Instead, record the space available around the proposed cylinder so the required expansion arrangement and controls can be accommodated during design.
The position depends on the unvented cylinder arrangement and applicable installation requirements. During the survey, record the existing tundish where present and the space and routes available for the final safety-discharge arrangement.
The final route needs to satisfy the applicable requirements and terminate appropriately. The survey should identify possible routes, changes in level, penetrations, obstructions and any existing discharge arrangement. Do not assume an existing pipe is suitable without further assessment.
Not necessarily. However, a cylinder is considerably heavier when full. Record the floor construction and condition where possible. Where structural adequacy is uncertain, it should be verified before installation.
Often, provided the location, structure, access, pipework, discharge arrangement and servicing requirements are suitable. An upstairs location should be surveyed in the same way as any other candidate cylinder position.
Potentially. The survey should record available space, environmental conditions, frost exposure, pipe routes, electrical provision, safety-discharge route and service access. The selected product and installation requirements can then be checked against the location.
Some installations may allow it, but a loft position needs careful assessment, including structural support, delivery access, future replacement, service access, pipe routes, safety discharge and environmental conditions. A loft should not be selected simply because there appears to be unused space.
It depends on the selected product. Measure the space available around the cylinder location first, then check the manufacturer’s installation and service requirements during design.
This varies according to the cylinder and immersion-heater arrangement. The important survey principle is to record the available withdrawal space rather than simply confirming that the immersion connection can be reached.
Useful photographs include whole cupboard, existing cylinder, cylinder label, left and right sides, space above, floor, primary pipework, domestic-water connections, tundish/discharge pipe, expansion vessel, immersion/electrical connections, cupboard doorway and restricted access route.
Yes, where realistic alternatives exist. Different locations can then be compared for space, access, pipework, safety discharge, servicing, floor support, electrical provision and household disruption.
A homeowner can often provide useful measurements, photographs and video through a structured self-survey. They should not be expected to identify technical components they do not understand, open electrical equipment or make technical decisions about the installation. The customer can provide the evidence. The installer and designer decide what that evidence means.
Survey the Complete Cylinder Installation Space
A useful cylinder-location survey should record cupboard dimensions, door dimensions, delivery and removal route, existing cylinder, primary connections, domestic-water connections, safety-discharge route, ancillary-component space, service clearance, electrical and immersion access, floor/support, household storage constraints, photos and any uncertainty.
The cylinder is only one component of the cylinder installation.
Measure the route into the cupboard as well as the space inside it.
The cupboard must fit the service space as well as the cylinder.
Do not survey the cylinder cupboard without surveying where a safety discharge can go.
The survey records the installation space. The design determines what cylinder belongs in it.
HEAT PUMP DESIGN SUPPORT
Send us the completed cylinder-location survey and we’ll select and size the cylinder against the actual space.
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