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Sime Rectangle Expansion Vessel 8 Litre 3/8 Inch Male 5183726

Sime

Sime Rectangle Expansion Vessel 8 Litre 3/8 Inch Male 5183726

Sime 8 litre rectangular expansion vessel with a 3/8 inch male connection, used across a range of Sime boiler models.

At a glance

  • Also known as N9079-1
Manufacturer part no.
5183726
Showing prices

£111.42

£92.85 ex. VAT · VAT at 20%

Available to order · 3 working days
Available to order · 3 working days
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 rectangle expansion vessel is an 8 litre diaphragm vessel with a 3/8 inch male connection, used in Sime domestic gas boilers. It absorbs the expansion of water as the heating system heats up, limiting pressure rise within the sealed circuit. This vessel is the rectangular format used in the Sime Ecomfort Plus and related appliance families.

Signs this part needs replacing

  • System pressure rises sharply as the boiler heats up and falls again once it cools
  • The pressure relief valve discharges water during normal heating cycles
  • The boiler loses pressure repeatedly and needs frequent topping up
  • Water is present at the vessel connection or the vessel feels heavy when removed
  • The diaphragm has failed, allowing water and air to mix within the vessel

Before you order

  • Confirm your boiler model and part number against the fitment list above
  • Check the existing vessel's capacity, shape and connection size match this part
  • Verify the 3/8 inch male thread matches the connection point on your appliance
  • Check there is clearance within the casing for a rectangular vessel of this size

Not sure which part?

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