SPECIAL OFFERS
Onyx 25L Red Heating Vessel 3/4 1.5 Bar
Onyx 25 litre red expansion vessel for sealed heating systems, with a 3/4 inch connection and 1.5 bar pre-charge.
At a glance
£29.42
£24.52 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 Onyx 25L red heating vessel is an expansion vessel for sealed central heating systems. It absorbs the change in water volume as the system heats, limiting the pressure rise seen at the boiler. The red casing identifies it as a heating circuit vessel rather than a domestic hot water unit, and it is supplied with a 3/4 inch connection and a 1.5 bar pre-charge.
Signs this part needs replacing
- Boiler pressure climbs quickly as the system heats, or the pressure relief valve discharges
- Water escapes from the Schrader valve when the charge is checked
- The vessel feels heavy or sounds full of water when tapped
- System pressure needs topping up frequently
- Corrosion, staining or weeping around the connection
Before you order
- Confirm the system connection is 3/4 inch
- Check the pre-charge pressure suits the system requirement (1.5 bar)
- Confirm the vessel is for a heating circuit, not domestic hot water
- Check the available space and how the vessel will be mounted
No specification data held for this part.
| Make | Model / assembly | Reference | Years | Fitment |
|---|---|---|---|---|
| SPECIAL OFFERS Pressure Vessels & Accessories | — | — | — |
Documents & drawings
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No documents held for this part. The technical team will source them from the manufacturer — usually the same working day.
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