Ariston Main Flow Switch DIA 27RFFI 998099

One of the most common heating complaints is that the radiators are working perfectly, but there is no hot water coming from the taps. This frustrating problem often points to a single, small component. This genuine Ariston Main Flow Switch DIA 27RFFI 998099 is a manufacturer-approved spare part designed to detect hot water demand and restart your boiler firing.

The Key to On-Demand Hot Water

Inside your Ariston combi boiler, the main water switch is a crucial sensor. Its sole job is to detect water movement when you turn on a hot tap. As soon as it senses this flow, it sends an electronic signal to the boiler's main circuit board (PCB), instructing it to ignite the burner and initiate water heating. It is a vital but straightforward process. When this switch works correctly, you get instant hot water, just as expected. When it fails, the boiler simply never receives the message that hot water is needed, so it remains inactive, even though the central heating side might work perfectly. The most common causes of failure are limescale build-up, especially in areas with hard water, which can cause the internal turbine or paddle to stick and stop spinning. Debris from the system can also cause a blockage, or it can simply fail due to years of constant service.

Diagnosing a faulty flow switch is a familiar task for a heating engineer. But the fix is only as good as the part you use. The Ariston Main Flow Switch DIA 27RFFI 998099 is the official OEM component, built to the specifications required for a seamless repair. A genuine part is essential because it guarantees the switch will send the correct signal to the PCB and fit perfectly within the pipework without leaks. Non-genuine parts can be notoriously unreliable, with incorrect electrical resistances that send confusing signals, or poor-fitting connections that can lead to intermittent faults or fail completely in a short space of time. Choosing the official Ariston spare ensures a dependable, first-time fix, maintaining the boiler's performance and safeguarding your professional reputation. It’s a commitment to quality that ensures the whole heating system functions as intended.

Replacing the faulty unit with a new Ariston Main Flow Switch DIA 27RFFI 998099 provides an immediate and lasting solution. The boiler will once again respond instantly to hot water demand, restoring comfort and convenience to the household. It is a fundamental repair that highlights the importance of every component, from the main controls down to the simplest plumbing fittings, working together in harmony. It brings a key function of the boiler back online, ensuring it runs efficiently and reliably for years to come, and solves one of the most common "no hot water" issues an engineer will face.

Technical Specifications

• Product Type: Main Flow Switch / Flow Sensor
• Manufacturer: Ariston
• Part Number (MPN): 998099
• Heating and Plumbing World SKU: 998099

Boiler parts can be particular to certain models and even serial number ranges. If you are unsure whether this is the correct part for an appliance, our expert team is here to provide assistance. You can reach us via our Contact Us page. Feel free to browse our full range of genuine spares and heating supplies here at Heating and Plumbing World.