Domakihub How to Install a Concealed Cistern: A Step-by-Step Guide
Understand the full installation process before your plumber arrives — or tackle it yourself if you are confident with pipework.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
A concealed cistern hides the water tank inside a stud wall or purpose-built frame, leaving only a flush plate visible — a look that suits the compact bathrooms found in Greek apartments, holiday villas, and boutique hotels alike. The video above walks through a real back-to-wall installation on a working site; this article translates those steps into a clear, ordered guide you can follow or use to brief your plumber. Water supply modifications should always be pressure-tested and, in rental or hotel properties, must comply with local building codes — when in doubt, bring in a licensed plumber.
What is a concealed cistern and why choose one?
A concealed cistern (also called an in-wall or hidden cistern) is a slim plastic tank housed inside a carrier frame that is fixed to the floor and wall studs. Once the frame is clad in tile backer board and tiled, only the toilet pan and a dual-flush plate are visible. The result is a minimalist finish that is easier to clean and frees up floor space — a real advantage in the narrow bathrooms typical of Greek island properties and urban apartments.
Most systems on the Greek market use standard European carrier frames (Geberit, Viega, TECEbase and their local equivalents are the most common). All use the same principle: a fill valve feeds the tank from a 15 mm cold-water supply, and a dual-flush pneumatic mechanism is triggered through push rods connected to the flush plate.
What the job actually involves — and when to call a pro
Installing a concealed cistern sits in the grey zone of DIY plumbing. Fixing the frame, hanging the pan, and connecting push rods are straightforward assembly tasks. The parts that require plumbing competence are isolating the existing water supply, extending or re-routing the cold-water feed to the frame's inlet, and pressure-testing the joint after connection. If your property uses a pressurised mains supply (common in mainland Greece) rather than a gravity header tank (common in older island buildings), an incorrect connection can cause significant water damage. A licensed plumber for the supply connection alone is strongly recommended for rental properties, hotels, or anywhere building regulations apply.
That said, understanding the full process allows you to prepare the rough-in correctly, order the right frame depth, and confirm the plumber's work before the wall is boarded up — saving costly callbacks.
Installing a Concealed Cistern: 5 Key Steps
- 1
Fix the carrier frame and mark rough-in positions
Stand the steel carrier frame in the correct position — typically 400–420 mm from the finished floor to the underside of the toilet horn, following the manufacturer's spec sheet. Check it is perfectly plumb and level on both axes, then drill and plug the floor fixings. Mark the wall behind for the cold-water inlet (usually at 180 mm from the floor for most European frames) and the waste outlet centre-line. The frame height is adjustable on most models, so confirm the toilet pan height before drilling.
- 2
Extend the cold-water supply and fit the fill valve
Turn off the cold-water supply at the nearest isolating valve (or at the mains stopcock if none exists). Using 15 mm copper or push-fit plastic pipe, run the supply to the inlet on the left side of the frame, finishing with a mini isolating valve so the cistern can be serviced without shutting off the whole bathroom. Push the fill valve through the cistern's side port and secure with its nut — do not overtighten. Connect the supply pipe to the valve's tail. At this stage the joint is exposed and easy to inspect, so turn the water back on briefly to check for drips before boarding.
- 3
Connect the waste outlet and hang the toilet pan
Fit the rubber gasket onto the cistern's flush outlet (the large port at the bottom of the tank). Slide the pan's inlet horn onto the rubber connector, aligning it with the pre-marked waste pipe centre. Most wall-hung pans bolt directly onto the frame's threaded studs with the supplied bolts and plastic distance pieces — do not crush the pan flange. Back-to-wall pans that sit on the floor are placed against the wall, with the waste spigot pushed into a standard 100 mm floor outlet. Either way, confirm the pan is level before final tightening.
- 4
Board, tile, and set the flush plate depth
Clad the frame with moisture-resistant tile backer board (12 mm cement board is standard), cutting a service access hatch or using the proprietary access frame supplied with the cistern. Tile the wall in the normal way, leaving the flush plate recess clear. Before the tiles go on, thread the two flush push rods down through the frame's guide tubes to confirm they move freely — this is much harder to fix after tiling. The flush plate recess depth is adjustable: most plates work at 13–15 mm from the face of the tile to the front of the frame, so measure before grouting.
- 5
Fit the flush plate, test, and adjust water volume
Snap or screw the flush plate into its recess. Press both buttons to confirm both flush volumes operate. Most fill valves have an adjustable float arm or clip to set the full-flush volume (typically 6 litres) and the half-flush volume (3 litres) — consult the valve's adjustment diagram to tune these. Check the pan rim for even water distribution on a full flush. Finally, inspect all supply joints once more with the system under normal working pressure, and leave the access panel label clearly marked for future servicing.
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FAQ
- Can I install a concealed cistern myself without a plumber?
- The frame assembly, boarding, and flush-plate fitting are within reach of a competent DIYer. However, modifying or extending the cold-water supply pipe — especially on a pressurised mains system — is a job that requires plumbing knowledge and, in rental or commercial properties in Greece, must comply with local building regulations. If you are unsure about the pipework, hire a licensed plumber for that part alone and handle the rest yourself.
- How deep does the wall need to be for a concealed cistern?
- Standard European carrier frames are 120 mm deep (measured from the finished wall face to the back wall). The frame itself is 80–100 mm, but you need room for tile backer board and tiles on top. Check your available wall depth before ordering — some brands offer slim-line frames at 80 mm overall for tight spaces, which is common in Greek apartment bathrooms.
- What happens if the concealed cistern leaks after the wall is tiled?
- All quality frames include either a proprietary access hatch or space for a tile-on access panel above or beside the pan. Through this opening you can reach the fill valve, flush valve, and supply connection for servicing without breaking tiles. Never board up a cistern without providing some form of access — it is both impractical and, in rental properties, a maintenance liability. If you discover a leak behind a fully sealed wall, call a plumber immediately: the longer a concealed leak runs, the more structural damage results.