Ariston
Ariston Expansion Vessel DHW 999403
Ariston DHW expansion vessel, part 999403, for Genus 27 series gas boilers.
At a glance
- Appliance family: Genus 27 series
- Also known as EXPANSION-VESSEL-35L, 1571220
£152.77
£127.31 ex. VAT · VAT at 20%
Same-day dispatch
Ordered by 4pm Mon–Fri, 10:30am Sat.
30-day returns
Unused, in original packaging.
What it is
The Ariston 999403 is a domestic hot water (DHW) expansion vessel fitted to Ariston Genus 27 series gas boilers. It absorbs the pressure rise created as water in the DHW circuit heats and expands. This is a service component for the appliance family listed below.
Signs this part needs replacing
- Water discharging from the pressure relief valve as the DHW circuit heats.
- DHW pressure fluctuating beyond its normal range during draw-off and recovery.
- Water staining or corrosion around the vessel body or its connection point.
- Falling DHW pressure requiring frequent manual top-ups.
- Reduced hot water delivery as the vessel no longer buffers expansion.
Before you order
- Check the boiler model against the fitment list above, as several entries are limited to specific serial number ranges.
- Read the serial number from the appliance data badge and confirm it falls within the relevant range.
- Confirm the fault lies with the DHW vessel rather than the heating circuit vessel.
- Check the vessel connection and mounting arrangement on the appliance before ordering.
Compliance
| Barcode / EAN | 5411692333003 |
|---|---|
| Alternative numbers | EXPANSION-VESSEL-35L, 1571220 |
| Make | Model / assembly | Reference | Years | Fitment |
|---|---|---|---|---|
| ARISTON ARISTON GENUS 27 BFFI PLUS - FROM SERIAL No 2320010200001 TO SERIAL No 2320020100002 | — | — | — | |
| ARISTON ARISTON GENUS 27 BFFI PLUS - FROM SERIAL No 2320020100002 TO SERIAL No 2320102500001 | — | — | — | |
| ARISTON ARISTON GENUS 27 BFFI PLUS - FROM SERIAL No 2320317800001 | — | — | — | |
| ARISTON ARISTON GENUS 27 PLUS - UP TO SERIAL No 2320020100001 | — | — | — | |
| ARISTON GENUS 27 BFFI PLUS LPG EDITION 1 (MAY 2000) | 47-116-11 | 47-116-11 | — | — |
| ARISTON GENUS 27 BFFI PLUS LPG EDITION 2 (OCT 2000) | 47-116-11 | 47-116-11 | — | — |
| ARISTON GENUS 27 BFFI PLUS LPG EDITION 3 (MAY 2001) | 47-116-11 | 47-116-11 | — | — |
| ARISTON GENUS 27 BFFI PLUS LPG EDITION 4 (OCT 2003) | 47-116-11 | 47-116-11 | — | — |
| ARISTON GENUS 27 BFFI PLUS NG EDITION 1 (MAY 2000) | 47-116-11 | 47-116-11 | — | — |
| ARISTON GENUS 27 BFFI PLUS NG EDITION 2 (OCT 2000) | 47-116-11 | 47-116-11 | — | — |
Showing 10 of 12 compatible appliances.
Documents & drawings
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