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Sime O-Ring Dalmar R12 6226421

Sime

Sime O-Ring Dalmar R12 6226421

Sime O-Ring Dalmar R12, part 6226421, for DHW heat exchanger sealing on compatible Sime gas boilers.

At a glance

  • Also known as O-RING-DALMAR-R12, 2040944
Manufacturer part no.
6226421
Showing prices

£1.93

£1.61 ex. VAT · VAT at 20%

Available to order · 1 working day
Available to order · 1 working day
Not certain it's the right part? The technical team verifies fitment before dispatch — no charge, and it stops a second trip.Call the technical teamSend a technical question

Same-day dispatch

Ordered by 4pm Mon–Fri, 10:30am Sat.

30-day returns

Unused, in original packaging.

What it is

The Sime O-Ring Dalmar R12 is a sealing O-ring for the domestic hot water (DHW) heat exchanger on Sime gas boilers. It is supplied under Sime part number 6226421 and is listed in the O-rings, washers and gaskets category. Its function is to seal the DHW heat exchanger connection and prevent water leakage.

Signs this part needs replacing

  • Water weeping or dripping from the DHW heat exchanger connection.
  • Visible flattening, cracking, hardening or perishing of the O-ring.
  • Scale, corrosion or debris around the sealing face.
  • Intermittent leaks that worsen when the boiler is running or after pressure changes.
  • Staining or water marks on components below the heat exchanger.

Before you order

  • Check your boiler model against the fitment list above.
  • Confirm the part number is 6226421.
  • Inspect the DHW heat exchanger sealing face for damage, scale or debris before fitting.
  • Isolate and depressurise the boiler before removing the existing O-ring.

Not sure which part?

Search by part number, product name or brand — our technical team confirms fitment before anything is dispatched.