Buttons to Suit Geberit Sigma 8 Cistern

What the Sigma 8 means on this page

The listings on this page call the concealed cistern the Geberit Sigma 8, and most of the Geberit plates here say they suit Sigma 8 cisterns. A flush plate has the same name as the cistern series it fits, and a plate for one series does not fit another. Confirm which cistern is behind your wall before you order. A plumber can read it once the old plate is off. For the full Geberit plate guide, see Geberit concealed toilet buttons, and for the cisterns and the suites sold with them see Geberit cistern and toilet suite packages.

Plates that name the Sigma 8

The Sigma 20 is an ABS plate in round and square shapes. Finishes include matte white, gloss white, white with gold or chrome trim, matte black, black with chrome, matte chrome and bright chrome, and a stainless steel and chrome version exists too. The Sigma 30 is ABS with a fingerprint resistant matte finish, in matte white, matte black and gloss white. The Sigma 60 is stainless steel with a glass finish in white or black, with a brushed chrome version as well. Most of these listings state that the plate is manufactured in Switzerland.

The listings do not all use the same words. Three Sigma 20 plates, in matte white, matte black and gloss white, say they suit Sigma cisterns without naming the Sigma 8. Two listings, the Sigma 20 white with chrome trim and the Sigma20 square in bright chrome, name no cistern at all. Check those with a plumber before you order.

Round or square

The Sigma 20 comes round and square. The square listings describe ABS construction, as the round ones do, and the fit comes from the Sigma series, not from the shape. Both are the same size on the wall in the brochure, 246mm by 164mm, so the opening you leave does not change. Choose the shape to suit the room.

Plates that suit a different cistern

The Kappa 50 plate in satin chrome pairs with the Geberit Kappa Under Counter 150 concealed cistern and is its access panel, so it is not a Sigma 8 plate. The Meir Sigma 21 plates are described as suitable for Sigma concealed in-wall cisterns. They are brass with a PVD finish, 246mm wide, 164mm high and 15mm deep, in brushed nickel, champagne, lustre bronze, tiger bronze and shadow.

The Meir Sigma 21 plates

The Meir plates are a different product from the Geberit plates beside them. The listings call them Meir's Sigma 21 dual flush plates by Geberit, made in Switzerland and assembled in Australia. The listing gives a weight of 2.2kg. It says a hand made PVD technique applies the finish, so colour and finish may vary slightly from piece to piece. If the plate has to match other Meir fittings in the room, order the plate and the fittings together and compare them in the same light.

Brass with a PVD finish needs different care from ABS. The Buildmat help centre advises cleaning brushed brass with a soft damp cloth and mild dish soap, wiping in the direction of the grain, then rinsing and drying with a soft cloth. It warns that water left on brushed brass causes mineral deposits that get harder to remove the longer they sit, and in hard water areas it suggests a quick wipe after each use. Avoid acidic cleaners, bleach and anything abrasive, it says, and do not use vinegar, which can damage the coating over time. Many bathroom spray cleaners are too harsh for these finishes, so keep them off the plate. Check the care instructions that come with the plate for anything specific to its finish.

What a Sigma8 is, and why the plate must match it

The Sigma8 is the Geberit in-wall cistern this page is built around. The Geberit Australia brochure shows it in two forms: a Sigma8 concealed cistern for a back to wall pan, and a Sigma8 concealed cistern with a frame for a wall hung pan, which is sold as the Duofix version. Each comes in a 3 star and a 4 star model with its own product code. The brochure lists the 4 star model at an average flush of 3.4 litres, from a 4.5 litre full flush and a 3 litre half flush. The 3 star model is listed at 3.8 litres, from a 6 litre full flush and a 3 litre half flush.

The brochure says all Sigma buttons are compatible with Sigma concealed cisterns, and its Sigma60, Sigma50, Sigma30, Sigma21 and Sigma20 pages each carry the line "Suits Sigma8 concealed cistern". That is why the plates on this page are collected here.

The Sigma8 is mechanical. The Reece installation instructions for the Duofix version describe a mechanical front press that suits pneumatic or electronic plates, so the plate type is a choice and not a limit of the cistern. The plates on this page are the mechanical type. If you want a remote, a pneumatic or a sensor plate on a Sigma8, ask the plumber which plate types suit the cistern behind your wall.

Mechanical, pneumatic and electronic plates compared

A Sydney Bathroomware guide to flush plates and cisterns sets out the three types. A mechanical plate, which it calls the most diverse and popular option, is reliable, easy to service and familiar to plumbers, and it offers the widest choice of cistern sizes and shapes. It does not suit a cistern that has to sit away from the toilet, such as in a ceiling space. A pneumatic plate moves air through hoses from the buttons to the valve, so the cistern can be remote, in a ceiling, a side wall or a cupboard, and two separate buttons can work without a backplate. The guide's trade-off for that minimalist look is that without a backplate you need access to the cistern from somewhere else. An electronic plate works by a hand wave, so nothing is touched, but the guide says it narrows the brands and cisterns you can choose. For a Sigma8 with a plate directly in front of it, mechanical is the straightforward match, and that is what the listings here are.

Where a Sigma8 sits in the wall

The brochure's installation drawings label the Sigma8 in-wall cistern 80mm and the Sigma8 Duofix 90mm, and a retailer listing describes the tank as fitting a standard 90mm wall. The Reece instructions list pre-wall, in-wall and stud installation at a minimum of 80mm, a load rating of 400kg for the wall hung version, and an operating pressure of 100 to 500kPa. Those figures are for the plumber and the builder, but they explain why you choose the plate with the wall in mind: the plate sits in the lining in front of the cistern. The brochure notes that the Sigma60 needs a minimum wall lining of 30mm to sit flush, and the same logic applies to any plate, so give the tiler the plate size from the spec sheet.

Sigma cisterns come in two depths

Geberit Great Britain's February 2026 assortment overview of Sigma plates for concealed cisterns lists two Sigma80 versions, one for the Sigma concealed cistern at 12 cm and one for the Sigma concealed cistern at 8 cm. The Sigma family has more than one depth, and the Sigma8 on this page is the 8 cm one. A plumbing forum thread on the 8 cm cistern makes the same point from the other side: plates are often advertised as fitting 8 cm or 12 cm cisterns without saying whether they fit both. The sticker code or the depth marked on the frame is the dependable check, and the listing should name the Sigma8 or the Sigma 8 cistern, as the Geberit listings on this page do.

Plate names change over time

The same Geberit Great Britain overview shows that plate names move. It lists the Sigma50 round as the former Sigma21, and the Sigma10 square and Sigma20 square as the former Sigma30. That is a UK document and the Australian names may differ, because the Geberit Australia brochure shows the Sigma21, Sigma30 and Sigma50 as separate designs. If you are matching an older plate by name, check the dimensions and finish against the current listing as well. The Australian brochure gives the Sigma20, Sigma21 and Sigma30 plates at 246mm by 164mm with a button depth of 12mm, the Sigma50 at the same width and height with a depth of 14mm, and the Sigma60 at 214mm by 132mm.

What the Geberit data sheets add

The Geberit data sheets for the Sigma20 plates describe front actuation with sound absorbing actuator rods and tool free fast adjustment, and a maximum actuation force of 20 newtons. They list accessories too: a DuoFresh module with automatic actuation, and an extension set for Sigma, Omega and Kappa concealed cisterns. The sheet for the matte white round plate gives 24.6 centimetres wide, 16.4 centimetres high and 1.2 centimetres deep, with a white matt, easy to clean coated button and a glossy white design ring, which matches the 246mm by 164mm in the brochure. The Sigma60 glass plate sheet is more restrictive. It suits Sigma concealed cisterns of 8 centimetres from the 2016 range, with covering thicknesses of 24mm to 50mm. It is not suitable for Geberit Duofix elements for wall hung toilets in barrier free applications, and it carries a note that the plate is phasing out. A tiled wall thicker than 50mm will not suit that plate, so ask the supplier about replacements before you rely on it.

Replacing a plate on a Sigma8

The Geberit listings say you lift off the old plate and drop the new plate in its place. Each box lists the flush plate and the installation instructions, and each listing links to the specification sheet. Geberit UK describes the equivalent job on a Sigma40: lift the plate off with gentle upward pressure, remove the actuator rods, release the frame, then fit the new frame, set the rods and snap the plate in with a click. It states that no tools are needed and one person can do it. The Sigma40 is not on this page, so treat those steps as a picture of the job and follow the instructions that come in the box for the plate you buy. If you are unsure of the cistern, ask a plumber, because the match is the first thing to get right.

Servicing the Sigma8 through the plate

The plate is how a plumber reaches the cistern. The Geberit Australia concealed cistern page says the service opening behind the plate lets the flush and fill valves be installed, removed or adjusted. The brochure says a remote button cannot be used to service the cistern, so separate access is required for those. The NSW Government plumbing advisory note 18/2022 says that cutting gyprock, or breaking tiled and waterproof elements, in the future is not considered appropriate access to something that must be accessible. In practice, that means the plate or an access panel has to be planned in before the wall is tiled. Replacing a plate like for like keeps the same access, and changing to a remote plate does not.

What retailer pages add about the Sigma8 cistern

Two Australian retailer pages give details of the cistern behind these plates. The Sydney Bathroomware page for the Sigma8 in-wall cistern lists a tank 80mm deep, 428mm wide and 625mm high, a blow moulded polyethylene shell, and a factory flush of 4.5 and 3 litres that can be set to 6 and 3 litres for retrofits. It says the 4 star model has the WELS registration L05087, that the flush plate unclips to reach the inlet and outlet valves so tiles do not need to be cut for servicing, and that the filling valve is sound absorbing. It lists the Sigma01, Sigma20, Sigma30 and Sigma50 plates and remote dual flush buttons as compatible, and says the cistern is designed mainly for wall faced pans, with wall hung toilets needing the separate Duofix Sigma8 frame.

The Burdens Bathrooms page for the Duofix Sigma8 cistern and frame describes a one piece blow moulded HDPE tank that suits S trap and P trap pans and fits standard 90mm walls, and says over 30 flush button designs are available in Australia. It repeats the 400kg load figure for the wall hung version. These are retailer descriptions, so check the numbers against the installation instructions in the box. Where they agree with the Geberit Australia brochure, on the 4.5 and 3 litre flush and the 400kg rating on the Reece instructions, you can rely on them more.

Where the sources disagree

The retailer pages do not all say the same thing. One retailer says the Sigma8 is compatible only with Geberit buttons, while the Sydney Bathroomware page lists the plates by Geberit series. Another sells a brass dual flush plate from a different maker as compatible with the Geberit Sigma8 concealed cistern. The Geberit listings on this page say only that their plates suit the Sigma 8. Geberit does not state that third party plates fit its cisterns, so this page lists the Geberit plates and the Meir Sigma 21 plates, which are sold as Sigma 21 plates by Geberit. If you want a plate from another maker, ask that maker to confirm the fit in writing and keep the answer with your plumbing records.

The listings also differ on where a plate is made. The Geberit listings on this page state manufacture in Switzerland, while the Sydney Bathroomware page for the Sigma 20 says designed in Switzerland and made in Germany. The place of manufacture matters for the fit only through the series and the dimensions, which the spec sheet states.

Plate sizes on the Sigma 20 listing

Sydney Bathroomware gives the Sigma 20 dimensions as 246mm wide and 164mm high, which matches the Geberit Australia brochure. It lists the finishes as black chrome, brushed stainless steel, chrome, gloss white, matt black and matt white, and links a spec sheet, an installation guide, a CAD file and care instructions, the same set of documents the TBS listings link. If your tiler or designer works from CAD drawings, ask for the file for the plate you choose before the lining is set out.

A checklist before you order a plate

Read the listing for the cistern it names, then read the cistern in your wall. Confirm that the cistern is a Sigma8 by the code on the sticker or the depth. Check the shape and finish against the spec sheet, and the plate size against the opening in the lining. Make sure the plate type, mechanical in the listings here, suits the way the cistern is fitted. If the cistern is a Sigma 12 cm or an older unit, look at the Geberit concealed toilet buttons page, where the plates are organised by series, and at the Geberit cistern and toilet suite packages page for the cisterns themselves.

See concealed toilet buttons for plates for other cisterns, in wall concealed toilets for what a concealed cistern needs from the wall, and the main toilets guide for choosing a suite.