SPECIAL OFFERS
Special Offers Onyx 35L Red Heating Vessel ONYX35LHEAT
Onyx 35 litre red heating expansion vessel with a 3/4 connection and 1.5 bar pre-charge for sealed heating systems.
At a glance
£47.88
£39.90 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 35L red heating vessel is a diaphragm expansion vessel from the Special Offers range, intended for sealed heating systems. It absorbs the expansion of heated water in a closed circuit, limiting pressure swings across the system. The vessel has a 35 litre capacity, a 3/4 connection and a 1.5 bar pre-charge.
Signs this part needs replacing
- System pressure rises sharply when the boiler heats up and falls again once it cools
- The pressure relief valve discharges water during normal heating cycles
- Water appears at the air valve when the valve core is depressed
- The vessel feels heavy or sounds full of water when tapped
- System pressure needs topping up frequently
Before you order
- Confirm the vessel volume required for the system
- Check the connection size matches the system pipework
- Check the pre-charge pressure suits the system design
- Check there is space for the vessel and its mounting position
No specification data held for this part.
| Make | Model / assembly | Reference | Years | Fitment |
|---|---|---|---|---|
| SPECIAL OFFERS Pressure Vessels & Accessories | — | — | — |
Documents & drawings
Everything we hold for this part. Where a document exists but we don't hold it, the technical team will source it from the manufacturer — usually the same working day.
No documents held for this part. The technical team will source them from the manufacturer — usually the same working day.
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