Short answer: A static pressure reading can look acceptable while the combi oven loses pressure during filling or cleaning. Test dynamic pressure and flow at the appliance during its real demand.
The static gauge looks acceptable but fill or automatic cleaning faults occur when demand starts. The common misconception is that a no-flow pressure reading proves the water supply is adequate. This article turns that assumption into specific checks that can be recorded on the drawing, survey or commissioning sheet.
Model-specific rule: Testing and remedial plumbing must comply with water regulations and the appliance manual. Where gas, electricity, refrigeration, guarded components, hot oil, pressure or safety controls are involved, use the appropriately competent engineer and never bypass a safety device.
Static pressure can hide restriction
With no flow, pressure can equalise through undersized pipework, a partly closed valve or a loaded filter. The restriction appears only when the oven opens its fill valve.
- Record static and dynamic pressure.
- Measure at the appliance connection.
- Check valve and filter pressure loss.
Simultaneous demand changes the result
Dishwashers, sinks and other combis can reduce available pressure during peak cleaning or preparation. An isolated early-morning test may miss the fault.
- Repeat with realistic water users operating.
- Record time and operating state.
- Check whether several units fault together.
Pressure and flow are not interchangeable
Adequate pressure through a small or restricted line may still deliver insufficient volume. Compare both values with the exact manufacturer requirement.
- Measure flow where the manual requires it.
- Confirm pipe size, length and fittings.
- Check treatment and backflow devices for restriction.
What the site evidence may show
| Observation | Hidden issue | Next check |
|---|---|---|
| Static gauge is acceptable | Pressure collapses on fill | Measure dynamically |
| Oven works alone | Faults during wash-up | Test simultaneous demand |
| Pressure seems adequate | Fill time remains slow | Verify flow and restrictions |
A practical verification sequence
- Confirm the exact duty and model. Record what the appliance or space must achieve at peak service and use the current model-specific installation information.
- Draw the complete interface. Include moving parts, service/removal access, connections, adjacent equipment and the real operator or trolley position.
- Measure under a representative condition. Static, empty or isolated tests can hide the issue. Record the operating state, value, unit and test point.
- Correct and prove. Repeat the same test after any change and retain the evidence with commissioning or O&M information.
Checks to record:
- Static and dynamic pressure.
- flow rate.
- pipe size/length.
- valve position.
- filter pressure drop.
- simultaneous users..
Explain dynamic pressure and flow, simultaneous water demand, undersized pipework, valves/filters and how to test at the appliance during its highest-demand function. The result should be a measurable decision rather than a generic note such as “allow sufficient space” or “services by others”.
Common mistakes to avoid
- Testing at the building inlet instead of the appliance.
- Recording pressure without the operating condition.
- Ignoring loaded filters and partly closed valves.
- Increasing pressure without checking component limits.
Frequently asked questions
When should dynamic pressure be tested?
During the function identified by the manufacturer, such as boiler fill or cleaning, and under representative site demand.
Can a booster pump solve the problem?
Only after the cause, required flow, backflow, pipework and control arrangement are correctly designed.
What should be recorded?
Value, unit, test point, instrument, appliance function and other water users operating.
Related Kitchen Install Guide reading
- How Low Water Pressure Causes Dishwasher and Combi-Oven Faults
- How Water Treatment Problems Damage Kitchen Equipment
- Commercial Kitchen Equipment Commissioning Documents
Record the installation detail before handover
Use the KIG 318 Commercial Kitchen Installation Checklist to record equipment interfaces, measured conditions, outstanding actions and acceptance evidence.
Sources and further guidance
- RATIONAL: iCombi Pro UK technical data
- Electrolux Professional: Combi-oven installation manual
- Water Regs UK: Backflow protection
Last reviewed: 14 August 2026. This article provides general commercial-kitchen design and installation information. It does not replace the exact manufacturer instructions, a site-specific design, risk assessment or work by competent specialists. Stop use and obtain competent help where equipment or services may be unsafe.