How to install tapware for a back-to-wall bathtub?

Do you dream of the clean lines of a freestanding model but need to work with limited space?

Choosing a back-to-wall bathtub is the ideal alternative for combining contemporary design with architectural practicality. Placed against the partition wall, this hybrid structure frees up valuable space while bringing the aesthetic of a true home wellness sanctuary.

However, the success of your layout depends on one crucial technical point: the installation of the tapware. Unlike a classic built-in model, the back-to-wall configuration requires specific plumbing and sealing rules under the apron to avoid any risk of hidden leaks.

Whether you are a meticulous DIY enthusiast or preparing your renovation project, this complete technical guide walks you through each step to complete your installation cleanly and ensure perfect long-term operation.

The tools and materials needed for installation

To complete the installation without making a mistake, careful preparation of your workspace is essential. A neat installation requires precise measuring tools and suitable tightening equipment to avoid damaging the threads of your bathtub mixer.

Here is the complete list of materials to prepare on the floor before starting the operation:

• A thermostatic or mechanical mixer fitted with its finishing escutcheons.
• A long spirit level (minimum 60 cm) to check the flatness of the tub and the alignment of the connectors.
• A powerful drill-driver fitted with a bi-metal hole saw adapted to the diameter of your cartridges if you choose a deck-mounted installation.
• A cartridge of high-quality, fungicidal and translucent sanitary silicone to create the watertight peripheral seal.
• A set of braided stainless-steel supply hoses with a minimum length of 100 cm to make technical access easier.
• A complete waste kit including the extra-flat trap, the bottom drain and the flexible connection pipe.
• An adjustable wrench, a set of open-end spanners, PTFE tape or flax hemp with jointing paste to seal the threads.

Good to know: the high-end acrylic used by our brand is particularly robust. However, when using a drill, make sure to apply a moderate rotation speed without exerting excessive pressure to obtain a clean, burr-free hole.

Where to place the tap: choosing the ideal position

The position of your bathtub tap depends directly on the technical configuration of your partition wall and your aesthetic expectations. In a small bathroom, this choice is decisive for optimising the space in your bathroom and ensuring optimal everyday comfort.

Option 1: the deck-mounted tap

This technical solution is the most common for back-to-wall models. Direct drilling of the acrylic bathtub makes it possible to hide all the plumbing and connections under the structure. The water supply comes from below via supply hoses that connect to the water waiting points in the floor or at the bottom of the partition, creating the look of a perfectly self-contained block.

Option 2: wall-mounted or concealed tapware

Fixed directly to the partition wall, wall-mounted tapware completely frees up the rim of the tub, making daily maintenance easier. The offset connectors are screwed onto the hot and cold water inlets integrated into the wall. This configuration requires anticipating the installation height (generally between 70 and 80 cm from the finished floor) before starting finishing work or installing shower wall panels.

Step 1: preparing the position and aligning the networks

The first phase of the installation consists of preparing the floor surface and checking the positioning of the waiting networks. Turn off the main water supply before starting any plumbing work.

• Position the bathtub dry in its final location against the partitions to mark the reference points with a pencil on the floor and on the wall.
• Using a spirit level, check that the floor is perfectly flat. If you are working on a wooden floor, make sure the mechanical structure can support the total load of the filled tub.
• Locate the 40 mm diameter PVC drain. To guarantee perfect flow and avoid any stagnation of wastewater under the tub, you must imperatively confirm the presence of a minimum slope of 2 cm per linear metre towards the main stack of the house.
• Adjust the height of the metal feet of the structure by screwing or unscrewing the threaded rods, then lock the counter-nuts using an open-end spanner to stabilise the base.

Step 2: connecting the mixer and assembling the waste system

Once the marks have been made, move the bathtub slightly away from the wall to create a comfortable working space and proceed with the hydraulic connections.

• If you have chosen a deck-mounted bathtub tap, apply masking tape to the acrylic to prevent slipping, then drill the holes using your hole saw at the diameter required by the mixer rods.
• Position the new mixer by inserting the supplied rubber sealing gaskets on the rim, then firmly tighten the fixing nuts from underneath using a box spanner.
• Connect the braided stainless-steel supply hoses to the mixer threads (left for hot water, right for cold water), making sure not to pinch or twist the pipes while tightening.
• Assemble the automatic waste system: fix the bottom drain fitted with its conical sealing gasket, then screw the extra-flat trap under the bathtub, making sure to orient the outlet towards your drainage pipe.

Step 3: positioning the bathtub, leak test and finishes

This third phase definitively seals the integration of your sanitary equipment into your bathroom.

• Move the bathtub close to its final position and connect the corrugated flexible drain hose from the trap to the PVC pipe using rigid PVC glue after sanding the ends.
• Connect the other end of the supply hoses to the wall or floor water inlets.
• Carry out the water test: open the main water supply and fill the bathtub completely. Let the water sit for around thirty minutes and pass a dry paper towel under all the connectors, the drain and the trap to check that there is absolutely no leak.
• Leave the bathtub full of water: its maximum weight will force the structure into its definitive low position. Clean and degrease the upper lip of the tub with household alcohol.
• Apply a regular and continuous bead of sanitary silicone between the edge of the bathtub and the tiled wall. Smooth the silicone joint in one single motion with a suitable tool dipped in soapy water.

Conclusion & maintenance: durability by Spalina

Taking care of your wellness space is child’s play thanks to the intrinsic properties of our high-end materials.

The pure acrylic selected by our French brand offers a perfectly smooth, non-porous and highly hygienic surface that prevents limescale and dirt from clinging year after year.

To maintain the glossy white shine of your tub and preserve the proper functioning of your bathtub mixer, absolutely avoid using aggressive chemical products, acidic strippers or abrasive sponges. Regular cleaning with a soft sponge soaked in warm water and neutral soap or diluted white vinegar is more than enough. Rinse with clean water after each use and wipe the tapware with a dry microfibre cloth to prevent water droplet marks.

By following these few installation and maintenance rules, you ensure a reliable and long-lasting installation.

Your questions about installing tapware on a back-to-wall bathtub

1. Where should the tap for a back-to-wall bathtub ideally be placed?

The ideal position depends on your space: a deck-mounted tap offers an integrated look and easier maintenance under the apron, while wall-mounted tapware completely frees up the rim of the tub for a refined design.

2. How do you connect a back-to-wall bathtub without an accessible inspection hatch?

The technical trick consists of using extra-long braided stainless-steel supply hoses (100 to 120 cm) and a flexible drain connection. This allows all bonding and tightening operations to be carried out while the bathtub is tilted onto its side, before lowering it vertically onto its feet.

3. What is the standard height for installing wall-mounted tapware?

For perfect comfort of use, the water inlets of a wall-mounted mixer should generally be positioned at a height between 70 and 80 cm from the finished floor, centred in relation to the width of the tub.

4. What hole saw diameter should be used for a deck-mounted tap?

The diameter depends on the brand of your mixer, but plumbing standards generally require drilling between 32 mm and 35 mm for the threaded rods of the cartridges or flexible hose connections.

5. Can a heavy thermostatic mixer be installed on an acrylic apron?

Yes, because the rims of high-end Spalina bathtubs have a reinforced frame underneath. Simply make sure to use the reinforcing plates and rubber gaskets supplied with the tap to distribute the tightening pressure evenly.

6. How can you make sure there is absolutely no leak under the tub after connection?

It is essential to carry out a water test by filling the bathtub completely before applying the finishing silicone joint. Let the water sit and carefully inspect the trap, the drain and the threads using dry absorbent paper.

7. How long should the sanitary silicone joint be left to dry?

It is necessary to let the silicone sealant cure for a minimum of 24 hours (48 hours being ideal for thick beads) before using your bath or splashing water onto the walls, while keeping the tub full throughout the drying phase.