Vaillant Boiler Ecotec Flow Sensor Replacement Spare Part

The Vaillant Eco Tec flow sensor detects hot water flow so the boiler fires when you open a tap. Over time, limescale or debris can affect the sensor and trigger false readings. As a result, you may get no hot water, cut outs, or temperature swings. Therefore, replacing the correct sensor restores accurate flow detection and improves stable hot water performance.

Compatibility :

• Ecotec Exclusive: 832 (VUW 32/4), 835 (VUW 356/5-7), 838 (VUW 386/4), 843 (VUW 436/5-7)
• Ecotec Plus 824 (VUW 246): /3-5, /5-5 (includes R1, R2/R3, R4 variants)\
• Ecotec Plus 825: VUW 196/5-5 R6, VUW 256/5-5 R4
• Ecotec Plus 831 (VUW 316): /3-5 (R1, R3, R5) + /5-5 (NG & LPG variants, includes R1, R2, R4)
• Ecotec Plus 832: VUW 246/5-5 R6 (NG & LPG), VUW 326/5-5 R4
• Ecotec Plus 835: VUW 306/5-5 R6, VUW 356/5-5 R4
• Ecotec Plus 837: VUW 376 (/3-5 R1, R3) + (/5-5, R1, R2, R4)
• Ecotec Plus 838: VUW 286/5-5 R6, VUW 386/5-5 R4
• Ecotec Plus 937: VUI 376 (/3-5) + (/5-5, R1, R2, R4)
• Ecotec Plus 938: VUI 286/5-5 R6, VUI 386/5-5 R4
• Ecotec Pro 24 (VUW 246): /3-3 (R1, R2) + /5-3 (R1, R2, R4, R6)
• Ecotec Pro 28: VUW 286 /3-3 (R1, R2) + /5-3 (NG & LPG, includes R1, R2, R4, R6)
• Ecotec Pro 30: VUW 306/5-3 R4

Important fitting advice

We recommend that all parts are fitted by a fully qualified Gas Safe registered engineer. If you need help confirming the right part, contact us our team has 10+ years of boiler spares knowledge and friendly chat support to help you quickly.

Delivery

At Boiler Spares Hub, we dispatch orders within 1 working day (Monday-Friday). Orders placed outside working days will be dispatched on the next working day. For delivery options available for this product, please add it to your basket or check our delivery options page.

Returns

We accept 30-day returns. Returns must be in an unopened, sealed box. If we find the item has been used or installation was attempted, we may refuse the return.

Frequently Asked Questions (FAQs)

1. What does the flow sensor do?
It detects hot water flow and signals the boiler to ignite and control output.

2. What symptoms suggest a faulty flow sensor?
No hot water, hot water cutting out, fluctuating temperatures, or delayed boiler response.

3. Can limescale affect this part?
Yes, limescale/debris can restrict movement or cause incorrect readings.

4. How do I confirm it’s the right part?
Match Vaillant part number 178988 with your boiler’s parts list/diagram and model.

5. Do I need an engineer to fit it?
If you’re unsure, use a qualified heating engineer to avoid leaks or incorrect fitting.